Surgical instrument with user adaptable techniques

ABSTRACT

A method for coagulating and dissecting tissue. The method includes measuring a tissue property and delivering multiple energy modalities to the tissue based on the tissue property. The energy modalities being delivered from a generator either alone or in combination.

PRIORITY

This application claims the benefit of U.S. Provisional Application Ser.No. 62/186,984 filed Jun. 30, 2015, U.S. Provisional Application Ser.No. 62/235,260, filed Sep. 30, 2015, U.S. Provisional Application Ser.No. 62/235,368, filed Sep. 30, 2015, U.S. Provisional Application Ser.No. 62/235,466, filed Sep. 30, 2015, U.S. Provisional Application Ser.No. 62/279,635, filed Jan. 15, 2016, and U.S. Provisional ApplicationSer. No. 62/330,669, filed May 2, 2016, the contents of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure generally relates to ultrasonic surgical systemsand, more particularly, to ultrasonic and electrosurgical systems thatallows surgeons to perform cutting and coagulation and adapt andcustomize techniques for performing such procedures based on the type oftissue being treated, employing multiple energy modalities based ontissue parameters, based on tissue impedance, and employing simultaneousenergy modalities based on tissue parameters.

BACKGROUND

Ultrasonic surgical instruments are finding increasingly widespreadapplications in surgical procedures by virtue of the unique performancecharacteristics of such instruments. Depending upon specific instrumentconfigurations and operational parameters, ultrasonic surgicalinstruments can provide substantially simultaneous cutting of tissue andhemostasis by coagulation, desirably minimizing patient trauma. Thecutting action is typically realized by an-end effector, or blade tip,at the distal end of the instrument, which transmits ultrasonic energyto tissue brought into contact with the end effector. Ultrasonicinstruments of this nature can be configured for open surgical use,laparoscopic, or endoscopic surgical procedures includingrobotic-assisted procedures.

Some surgical instruments utilize ultrasonic energy for both precisecutting and controlled coagulation. Ultrasonic energy cuts andcoagulates by vibrating a blade in contact with tissue. Vibrating athigh frequencies (e.g., 55,500 times per second), the ultrasonic bladedenatures protein in the tissue to form a sticky coagulum. Pressureexerted on tissue with the blade surface collapses blood vessels andallows the coagulum to form a hemostatic seal. The precision of cuttingand coagulation is controlled by the surgeon's technique and adjustingthe power level, blade edge, tissue traction, and blade pressure.

Electrosurgical devices for applying electrical energy to tissue inorder to treat and/or destroy the tissue are also finding increasinglywidespread applications in surgical procedures. An electrosurgicaldevice typically includes a hand piece, an instrument having adistally-mounted end effector (e.g., one or more electrodes). The endeffector can be positioned against the tissue such that electricalcurrent is introduced into the tissue. Electrosurgical devices can beconfigured for bipolar or monopolar operation. During bipolar operation,current is introduced into and returned from the tissue by active andreturn electrodes, respectively, of the end effector. During monopolaroperation, current is introduced into the tissue by an active electrodeof the end effector and returned through a return electrode (e.g., agrounding pad) separately located on a patient's body. Heat generated bythe current flowing through the tissue may form hemostatic seals withinthe tissue and/or between tissues and thus may be particularly usefulfor sealing blood vessels, for example. The end effector of anelectrosurgical device also may include a cutting member that is movablerelative to the tissue and the electrodes to transect the tissue.

Electrical energy applied by an electrosurgical device can betransmitted to the instrument by a generator in communication with thehand piece. The electrical energy may be in the form of radio frequency(“RF”) energy. RF energy is a form of electrical energy that may be inthe frequency range of 200 kilohertz (kHz) to 1 megahertz (MHz). Inapplication, an electrosurgical device can transmit low frequency RFenergy through tissue, which causes ionic agitation, or friction, ineffect resistive heating, thereby increasing the temperature of thetissue. Because a sharp boundary is created between the affected tissueand the surrounding tissue, surgeons can operate with a high level ofprecision and control, without sacrificing un-targeted adjacent tissue.The low operating temperatures of RF energy is useful for removing,shrinking, or sculpting soft tissue while simultaneously sealing bloodvessels. RF energy works particularly well on connective tissue, whichis primarily comprised of collagen and shrinks when contacted by heat.

The RF energy may be in a frequency range described in EN60601-2-2:2009+A11:2011, Definition 201.3.218-HIGH FREQUENCY. Forexample, the frequency in monopolar RF applications may be typicallyrestricted to less than 5 MHz. However, in bipolar RF applications, thefrequency can be almost anything. Frequencies above 200 kHz can betypically used for monopolar applications in order to avoid the unwantedstimulation of nerves and muscles that would result from the use of lowfrequency current. Lower frequencies may be used for bipolarapplications if the risk analysis shows the possibility of neuromuscularstimulation has been mitigated to an acceptable level. Normally,frequencies above 5 MHz are not used in order to minimize the problemsassociated with high frequency leakage currents. Higher frequencies may,however, be used in the case of bipolar applications. It is generallyrecognized that 10 mA is the lower threshold of thermal effects ontissue.

A challenge of using these medical devices is the inability to controland customize the power output depending on the type of tissue beingtreated by the devices. It would be desirable to provide a surgicalinstrument that overcomes some of the deficiencies of currentinstruments. The surgical system described herein overcomes thosedeficiencies.

SUMMARY

In one aspect, a surgical instrument for coagulating and dissectingtissue is provided. The surgical instrument comprising a processor; anend effector at a distal end of the surgical instrument, the endeffector configured to interact with tissue, the end effectorcomprising: a clamp arm; an ultrasonic blade; a force sensor incommunication with the processor and configured to measure a forceapplied to tissue located between the clamp arm and the ultrasonicblade; and a temperature sensor in communication with the processor; anultrasonic transducer acoustically coupled to the ultrasonic blade andconfigured to receive a drive signal from a generator to causeultrasonic motion of the ultrasonic blade and deliver energy to theultrasonic blade; wherein the processor is configured to: determine atype of tissue interacting with the end effector based on a tissuecoefficient of friction, wherein the tissue coefficient of friction isdetermined based on the force applied to the tissue by the end effector,the ultrasonic motion of the ultrasonic blade, and a rate of heatgenerated by the end effector; and dynamically control the drive signaldelivered to the ultrasonic transducer based on the type of tissueinteracting with the end effector.

In one aspect, a method for detecting a short circuit in a surgicalsystem configured to apply radio frequency energy and ultrasonic energyto a target surgical site is provided. The method comprises applyingradio frequency (RF) energy with an end effector to the target surgicalsite; transitioning from applying the RF energy to applying ultrasonicenergy with the end effector to the target surgical site; transmittingan exploratory ultrasonic pulse to the surgical site; measuring anultrasonic property about the ultrasonic pulse upon transmission to thesurgical site; determining whether the ultrasonic property is consistentwith a behavior of low impedance tissue when ultrasonic energy isapplied to the low impedance tissue; and continuing to apply ultrasonicenergy to cut the low impedance tissue if it is determined that theultrasonic property is consistent with ultrasonic energy being appliedto low impedance tissue.

According to aspects of the present application, during tissuetreatment, a parameterized tissue model can be fitted to the tissue. Theparameters that are found in the model can be used to generate anoptimal controller in real-time and could also be correlated to specifictissue characteristics. The present application provides real-timeoptimization on a generator control system based on RF impedance andreal-time tissue evaluation.

According to aspects of the present application, methods of systemidentification may be used to model the tissue in real-time and developcontrollers in real-time, specific to a particular tissue type tomaximize sealing, minimize sticking of tissue, and cycle times.Furthermore, control of the output of a surgical instrument based ontissue characteristics and changes in tissue during sealing and cuttingcycles is provided.

According to one aspect, a surgical instrument uses an RF energymodality to sense tissue characteristics, such as impedance, and thechanges of the tissue characteristics to modulate the output power of anultrasonic tissue treating system. Specifically, the output power of asurgical instrument may be modulated as a function of a desiredimpedance trajectory where the impedance trajectory results in a desiredtissue effect or outcome. In one aspect, the RF output may betherapeutic, e.g. tissue treating, or sub-therapeutic, e.g. sensingonly. The RF output may be applied to the tissue and the voltage andcurrent, or representations of the voltage and current, are measured orestimated. The impedance may be calculated by determining the ratio ofthe voltage to the current.

In addition, RF impedance is known to change during the heating andcoagulation of tissue. RF impedance can be used as an indicator of thestate of the tissue and therefore can be used to indicate progress in acoagulation cycle, vessel sealing cycle, cutting etc. An extension ofthis change in RF impedance can be used to form a desired treatmentcycle if the output is modulated such that the RF impedance follows aparticular, desired course of change in impedance. The desired course ofimpedance can be pre-determined based on the instrument's operatingparameters or determined by selection of the surgeon or measurement oftissue parameters to set this course of treatment. The course ofimpedance can determine one or more of the output power, output waveformor waveshape, selection of energy mode or modality or a point toterminate the application of energy to tissue.

In one aspect, a surgical energy generator system is disclosed, thesystem comprises an ultrasonic output stage configured to drive atransducer coupled to a tissue treating portion of a surgicalinstrument, where the tissue treating portion applies vibrational energyto tissue to affect treatment of that tissue and vibration amplitude ofthe tissue treating portion is controlled by a controller; an RF outputstage configured to supply electrosurgical energy to the tissue via atleast one electrode configured to apply electrosurgical energy to thetissue; sensing circuitry configured to measure impedance of the tissue;and a controller programmed to determine whether a tissue reaction hasoccurred as a function of impedance values and a predetermined rise inimpedance, where the tissue reaction corresponds to a boiling point oftissue fluid, to generate a target impedance trajectory as a function ofmeasured impedance and a predetermined desired rate of change ofimpedance based on the tissue reaction determination, where the targetimpedance trajectory includes a plurality of target impedance values foreach of a plurality of timesteps, and to drive tissue impedance alongthe target impedance trajectory by adjusting the output level of theultrasonic output stage to substantially match tissue impedance to acorresponding target impedance value for at least a predeterminedminimum time period.

In one aspect, an apparatus is provided for dissecting and coagulatingtissue. The apparatus comprises: a surgical instrument having an endeffector configured to interact with a tissue at a distal end thereof; agenerator electrically coupled to the surgical instrument and configuredto deliver radio frequency (RF) energy and ultrasonic energy to the endeffector to allow the end effector to interact with the tissue; whereinthe energy delivered to the end effector switches between RF energy andultrasonic energy based on a determination of a tissue impedance of thetissue interacting with the end effector such that the generatorswitches from RF energy to ultrasonic energy when the tissue impedancereaches a threshold level.

In addition to the foregoing, various other method and/or system and/orprogram product aspects are set forth and described in the teachingssuch as text (e.g., claims and/or detailed description) and/or drawingsof the present disclosure.

The foregoing is a summary and thus may contain simplifications,generalizations, inclusions, and/or omissions of detail; consequently,those skilled in the art will appreciate that the summary isillustrative only and is NOT intended to be in any way limiting. Otheraspects, features, and advantages of the devices and/or processes and/orother subject matter described herein will become apparent in theteachings set forth herein.

In one or more various aspects, related systems include but are notlimited to circuitry and/or programming for effecting herein-referencedmethod aspects; the circuitry and/or programming can be virtually anycombination of hardware, software, and/or firmware configured to affectthe herein-referenced method aspects depending upon the design choicesof the system designer. In addition to the foregoing, various othermethod and/or system aspects are set forth and described in theteachings such as text (e.g., claims and/or detailed description) and/ordrawings of the present disclosure.

Further, it is understood that any one or more of thefollowing-described forms, expressions of forms, examples, can becombined with any one or more of the other following-described forms,expressions of forms, and examples.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

FIGURES

The novel features of the described forms are set forth withparticularity in the appended claims. The described forms, however, bothas to organization and methods of operation, may be best understood byreference to the following description, taken in conjunction with theaccompanying drawings in which:

FIG. 1 illustrates one aspect of a surgical system comprising agenerator and various surgical instruments usable therewith;

FIG. 2 is a diagram of one aspect of the ultrasonic surgical instrumentof FIG. 16;

FIG. 3 is a diagram of one aspect of the surgical system of FIG. 16;

FIG. 4 is a model illustrating one aspect of a motional branch current;

FIG. 5 is a structural view of one aspect of a generator architecture;

FIG. 6 illustrates one aspect of a drive system of a generator, whichcreates the ultrasonic electrical signal for driving an ultrasonictransducer;

FIG. 7 illustrates one aspect of a drive system of a generatorcomprising a tissue impedance module;

FIG. 8 illustrates one aspect of a generator for delivering multipleenergy modalities to a surgical instrument;

FIG. 9 is an example graph of two waveforms of energy from one aspect ofa generator;

FIG. 10 is an example graph of the sum of the waveforms of FIG. 9;

FIG. 11 is an example graph of sum of the waveforms of FIG. 9 with theRF waveform dependent on the ultrasonic waveform;

FIG. 12 is an example graph of the sum of the waveforms of FIG. 9 withthe RF waveform being a function of the ultrasonic waveform;

FIG. 13 is an example graph of a complex RF waveform;

FIG. 14 illustrates one aspect of an end effector comprising RF datasensors located on the clamp arm;

FIG. 15 illustrates one aspect of the flexible circuit shown in FIG. 14in which the sensors may be mounted to or formed integrally therewith;

FIG. 16 is a cross-sectional view of the flexible circuit shown in FIG.15;

FIG. 17 illustrates one aspect of a segmented flexible circuitconfigured to fixedly attach to a clamp arm of an end effector;

FIG. 18 illustrates one aspect of a segmented flexible circuitconfigured to mount to a clamp arm of an end effector;

FIG. 19 illustrates one aspect of an end effector configured to measurea tissue gap G_(T);

FIG. 20 illustrates one aspect of a left-right segmented flexiblecircuit;

FIG. 21 illustrates one aspect of an end effector comprising segmentedflexible circuit as shown in FIG. 20;

FIG. 22 illustrates the end effector shown in FIG. 21 with the clamp armclamping tissue between the clamp arm and the ultrasonic blade;

FIG. 23 illustrates graphs of energy applied by the right and left sideof an end effector based on locally sensed tissue parameters;

FIG. 24 illustrates a graph depicting one aspect of adjustment ofthreshold due to the measurement of a secondary tissue parameter such ascontinuity, temperature, pressure, and the like;

FIG. 25 is a cross-sectional view of one aspect of a flexible circuitcomprising RF electrodes and data sensors embedded therein;

FIG. 26 is a cross-sectional view of one aspect of an end effectorconfigured to sense force or pressure applied to tissue located betweena clamp arm and an ultrasonic blade;

FIG. 27 is a schematic diagram of one aspect of a signal layer of aflexible circuit;

FIG. 28 is a schematic diagram of sensor wiring for the flexible circuitshown in FIG. 27;

FIG. 29 is a schematic diagram of one aspect of an RF energy drivecircuit;

FIG. 30 is a graphical representation of measuring tissue gap at apreset time;

FIG. 31 is a time to preset force versus time graph for thin, medium,and thick tissue types;

FIG. 32 is a graphical depiction of a graph of three curves, where thefirst curve represents power (P), voltage(V_(RF)), and current (I_(RF))versus tissue impedance (Z), the second curve and third curve representtissue impedance (Z) versus time (t);

FIG. 33 is a plan view of one aspect of an end effector;

FIG. 34 is a side view of the end effector shown in FIG. 33 with apartial cut away view to expose the underlying structure of the clamparm and an ultrasonic blade;

FIG. 35 is partial sectional view of the end effector shown in FIGS. 33,34 to expose the ultrasonic blade and right and left electrodes,respectively;

FIG. 36 is a cross-sectional view taken at section 36-36 of the endeffector shown in FIG. 33;

FIG. 37 is cross-sectional view taken at section 37-37 of the endeffector shown in FIG. 33;

FIG. 38 is a cross-sectional view taken at section 36-36 of the endeffector shown in FIG. 33, except that the ultrasonic blade has adifferent geometric configuration;

FIG. 39 is cross-sectional view taken at section 37-37 of the endeffector shown in FIG. 33, except that the ultrasonic blade has adifferent geometric configuration;

FIG. 40 is a cross-sectional view taken at section 36-36 of the endeffector shown in FIG. 33, except that the ultrasonic blade has adifferent geometric configuration;

FIG. 41 is cross-sectional view taken at section 37-37 of the endeffector shown in FIG. 33, except that the ultrasonic blade has adifferent geometric configuration;

FIG. 42A is a graphical representation of one aspect of a medical devicesurrounding tissue;

FIG. 42B is a graphical representation of one aspect of a medical devicecompressing tissue;

FIG. 43A is a graphical representation of one aspect of a medical devicecompressing tissue;

FIG. 43B also depicts example forces exerted by one aspect of anend-effector of a medical device compressing tissue;

FIG. 44 illustrates a logic diagram of one aspect of a feedback system;

FIG. 45 is a graph of power versus force as measured with a plurality ofplot points for various tissue types;

FIG. 46 is another graph of power versus force as measured with aplurality of plot points for various tissue types;

FIG. 47 is a logic flow diagram of one aspect of dynamically changingthe energy delivered to a surgical instrument based on a determinationof tissue type being treated by the instrument;

FIG. 48 is a logic flow diagram of one aspect of dynamically changingthe energy delivered to a surgical instrument based on a determinationof tissue type being treated by the instrument;

FIG. 49 is a logic flow diagram of one aspect of a method of dynamicallychanging the energy delivered to a surgical instrument based on adetermination of the hydration level of tissue being treated by asurgical instrument;

FIG. 50 is a logic flow diagram of one aspect of a method of dynamicallychanging energy being delivered from a generator based on the type oftissue being treated by a surgical instrument and variouscharacteristics of the tissue;

FIG. 51 is a logic flow diagram of one aspect of a technique fordynamically changing the energy delivered from a generator based onaperture defined by the end effector and energy parameters;

FIG. 52 is a logic flow diagram of one aspect of a technique fordynamically changing the energy delivered from a generator based onaperture defined by the end effector and energy parameters;

FIG. 53 is a logic flow diagram of one aspect of a dynamic tissuesensing technique;

FIG. 54 is a logic flow diagram of one aspect of a process for sealingor sealing and cutting large vessels or large tissue bundles;

FIG. 55 is a logic flow diagram of one aspect of a process for sealingor sealing and cutting large vessels or large tissue bundles bydynamically changing energy being delivered from the generator duringthe treatment of the tissue based on the changing aperture defined bythe end effector;

FIG. 56 is a logic flow diagram of one aspect of a process for sealingor sealing and cutting large vessels or large tissue bundles bydynamically communicating energy parameters to the generator during thetreatment of the tissue based on the changing aperture defined by theend effector of the surgical instrument;

FIG. 57 is a logic flow diagram of a technique to seal or seal and cutvessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements and the aperture defined by the clamp jawmeasurements;

FIG. 58 is a logic flow diagram of one aspect of a method of dynamicallychanging the energy delivered to a surgical instrument based on adetermination of a state of coagulation of tissue being treated by thesurgical instrument;

FIG. 59 is a logic flow diagram of a technique to seal or seal and cutvessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements;

FIG. 60 is a logic flow diagram of a technique to seal or seal and cutvessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements and the aperture defined by the clamp jawmeasurements;

FIG. 61 is a logic flow diagram of a technique for distinguishing ashort circuit from low impedance tissue while utilizing RF energy bymeasuring voltage properties of an exploratory ultrasonic pulse;

FIG. 62 is a logic flow diagram of a technique for distinguishing ashort circuit from low impedance tissue while delivering RF energy andmeasuring acoustic properties of an exploratory ultrasonic pulse,according to some aspects;

FIG. 63 is a logic flow diagram of a technique for conducting a tissuesealing technique without cutting by using a combination of ultrasonicenergy and RF energy, according to some aspects;

FIG. 64 is a logic flow diagram of a technique for conducting a tissuesealing technique without cutting by using a combination of ultrasonicenergy and RF energy, according to some aspects;

FIG. 65 is logic flow diagram of a technique for detecting low impedancetissue or metal shorts that may cause false short circuits in RF mode;

FIG. 66 is a timing diagram of a seal only pulse sequence illustrating abasic configuration of pulsing RF and ultrasonic energy for “Seal Only”mode;

FIG. 67 is a timing diagram of a seal only pulse sequence illustrating abasic configuration of pulsing RF and ultrasonic energy for “Seal Only”mode;

FIG. 68 is a timing diagram of a seal only pulse sequence;

FIG. 69 is a timing diagram of a seal only pulse sequence;

FIG. 70 is a timing diagram of a seal and cut pulse sequence, whichbegins and ends with ultrasonic energy pulses delivered at the sameamplitude during the sealing a cutting cycles;

FIG. 71 is a timing diagram of a seal and cut pulse sequence, whichbegins and ends with ultrasonic energy pulses delivered at variableamplitude during the sealing a cutting cycles;

FIG. 72 is a timing diagram of a seal only pulse sequence where theultrasonic energy pulse current is be set based on the impedancemeasured with the preceding RF energy pulse;

FIG. 73 is a logic flow diagram of a technique for delivering pulses ofdifferent energy modalities to tissue;

FIG. 74 is a logic flow diagram of a technique for delivering pulses ofdifferent energy modalities to tissue;

FIG. 75 is a logic flow diagram of a technique for delivering pulses ofdifferent energy modalities to tissue;

FIG. 76 is a logic flow diagram of one aspect of a process of applyingsimultaneous activation of different energy modalities to tissue;

FIG. 77 is a graphical representation of RF Impedance versus Time inconnection with the logic flow diagram of FIG. 67 to illustrate theultrasonic termination impedance;

FIG. 78 illustrates an example of the quality of a seal made in a vesselusing the simultaneous activation of RF and ultrasonic energy modalitiesas described in connection with FIGS. 76 and 77;

FIG. 79 is a graphical representation of seal burst pressure of carotidbundles versus an RF only seal and a simultaneous RF/ultrasonic seal asdescribed in connection with FIGS. 76-78;

FIG. 80 is a logic flow diagram of a process of simultaneous activationof RF and ultrasonic energy modalities;

FIG. 81 is a block diagram of one aspect describing the selection andapplication of composite load curves in a tissue seal control process;

FIG. 82 illustrates one aspect of a neural network for controlling agenerator;

FIG. 83 is an example graph showing RF impedance versus time of tissueimpedance at which a proper tissue seal is achieved using RF energy;

FIG. 84 is a graphical representation of RF impedance versus time oftissue impedance with 40 W of RF power delivered to tissue using adownhill simplex technique for a model of tissue and experimental data;

FIG. 85 is a graphical representation of RF impedance versus time oftissue impedance using a linear quadratic controller (LQR) withprecompensation to achieve steady state at a tissue impedance equal to250 Ohms for a model of tissue and experimental data;

FIG. 86 is a graphical representation of RF impedance versus time oftissue impedance using a linear quadratic controller (LQR) withprecompensation to achieve steady state at a tissue impedance that risesat a rate of 50 Ohms/second for a model of tissue and experimental data;

FIG. 87 is a logic flow diagram of a method for identifying a tissuetype and developing a control process to control the application of anenergy modality to the tissue according to tissue impedance;

FIG. 88 is a logic flow diagram of a method for treating tissue based ontissue impedance according to one aspect of the present disclosure;

FIG. 89 is a graphical depiction of a tissue impedance functionrepresented as tissue impedance |Z| (Ohms) as a function of time (Sec)showing one aspect of a termination impedance at which a proper tissueseal is achieved utilizing RF energy;

FIG. 90 is a logic flow diagram of one aspect of a method of dynamicallychanging the energy delivered to a surgical instrument based on adetermination of a tissue impedance of tissue being treated by asurgical instrument;

FIG. 91A is a graphical depiction of power and impedance as a functionof time delivered from a generator to an end effector of a surgicalinstrument;

FIG. 91B is a graphical depiction of voltage and current as a functionof time delivered from a generator to an end effector of a surgicalinstrument;

FIG. 91C is a graphical depiction of power, impedance, voltage, andcurrent as a function of time delivered from a generator to an endeffector of a surgical instrument as shown in FIGS. 91A and 91B;

FIG. 92 is a logic flow diagram of one aspect of a process of applyingsimultaneous activation of different energy modalities to tissue;

FIG. 93 is a graphical depiction of an RF tissue impedance functionrepresented as RF tissue impedance (Ohms) as a function of time (Sec) inconnection with the logic flow diagram of FIG. 92 to illustrate theultrasonic and RF termination impedance;

FIG. 94 illustrates an example of the quality of a seal made in a vesselutilizing simultaneous activation of RF and ultrasonic energy modalitiesas described in connection with FIGS. 92 and 93;

FIG. 95 is a boxplot graphic comparison of the burst pressure of acarotid artery seal made utilizing: (1) simultaneous application of RFand ultrasonic energy and (2) application of RF energy only as describedin connection with FIGS. 92-94;

FIG. 96 is a boxplot graphic comparison of the burst pressure of acarotid artery bundle seal made utilizing: (1) simultaneous applicationof RF and ultrasonic energy and (2) application of RF energy only asdescribed in connection with FIGS. 92-94;

FIG. 97 is a boxplot graphic comparison of the burst pressure of athyrocervical artery seal made utilizing: (1) simultaneous applicationof RF and ultrasonic energy and (2) application of RF energy only asdescribed in connection with FIGS. 92-94;

FIG. 98 is a boxplot graphic comparison of the burst pressure of acarotid artery bundle seal made utilizing simultaneous application of:(1) RF and lower ultrasonic energy and (2) RF energy and higherultrasonic energy as described in connection with FIGS. 92-94;

FIG. 99 is a boxplot graphic comparison of the burst pressure of acarotid artery bundle seal made utilizing simultaneous application of RFand ultrasonic energy at different termination impedances as describedin connection with FIGS. 92-94;

FIG. 100 is an example of a vessel with a partial seal made utilizingsimultaneous application of RF and ultrasonic energy and a partialtransection made utilizing ultrasonic energy;

FIG. 101 is a graphical depiction of an RF tissue impedance functionrepresented as RF tissue impedance (Ohms) as a function of time (Sec)and an ultrasonic current function represented as ultrasonic current(mA) as a function of time (Sec) during a “seal only” modality;

FIG. 102 is logic flow diagram of one aspect of a technique forsimultaneous activation of RF and ultrasonic energy and modulating theultrasonic energy to achieve a seal only process;

FIG. 103 is a graphical depiction of an RF tissue impedance functionrepresented as RF tissue impedance (Ohms) as a function of time (Sec)and an ultrasonic current function represented as ultrasonic current(mA) as a function of time (Sec) during a “seal and cut” modality;

FIG. 104 is logic flow diagram of one aspect of a technique forsimultaneous activation of RF and ultrasonic energy and modulating theultrasonic energy to achieve a seal and cut process;

FIG. 105A is a graphical depiction of an ultrasonic current functionsrepresented as ultrasonic current I_(h) (Amperes) delivered to theultrasonic transducer as a function of RF tissue impedance Z (Ohms) forvarious n values;

FIG. 105B is a graphical depiction of an ultrasonic current functionsrepresented as ultrasonic current I_(h) (Amperes) delivered to theultrasonic transducer as a function of RF tissue impedance Z (Ohms) forvarious n values;

FIG. 106 is a graphical depiction of multiple ultrasonic functionsrepresented as functions of time; and

FIG. 107 is a graphical depiction of constant RF power that was inputtedinto Equation 9 with RF energy terminated at 500 Ohm terminal impedance.

DESCRIPTION

Before explaining various forms of surgical instruments in detail, itshould be noted that the illustrative forms are not limited inapplication or use to the details of construction and arrangement ofparts illustrated in the accompanying drawings and description. Theillustrative forms may be implemented or incorporated in other forms,variations and modifications, and may be practiced or carried out invarious ways. Further, unless otherwise indicated, the terms andexpressions employed herein have been chosen for the purpose ofdescribing the illustrative forms for the convenience of the reader andare not for the purpose of limitation thereof.

Further, it is understood that any one or more of thefollowing-described forms, expressions of forms, examples, can becombined with any one or more of the other following-described forms,expressions of forms, and examples.

Various forms are directed to improved ultrasonic and/or electrosurgical(RF) instruments configured for effecting tissue dissecting, cutting,and/or coagulation during surgical procedures. In one form, a combinedultrasonic and electrosurgical instrument may be configured for use inopen surgical procedures, but has applications in other types ofsurgery, such as laparoscopic, endoscopic, and robotic-assistedprocedures. Versatile use is facilitated by selective use of ultrasonicand RF energy.

The various forms will be described in combination with an ultrasonicinstrument as described herein. Such description is provided by way ofexample, and not limitation, and is not intended to limit the scope andapplications thereof. For example, any one of the described forms isuseful in combination with a multitude of ultrasonic instrumentsincluding those described in, for example, U.S. Pat. Nos. 5,938,633;5,935,144; 5,944,737; 5,322,055; 5,630,420; and 5,449,370.

As will become apparent from the following description, it iscontemplated that forms of the surgical instruments described herein maybe used in association with an oscillator unit of a surgical system,whereby ultrasonic energy from the oscillator unit provides the desiredultrasonic actuation for the present surgical instrument. It is alsocontemplated that forms of the surgical instrument described herein maybe used in association with a signal generator unit of a surgicalsystem, whereby electrical energy in the form of radio frequencies (RF),for example, is used to provide feedback to the user regarding thesurgical instrument. The ultrasonic oscillator and/or the signalgenerator unit may be non-detachably integrated with the surgicalinstrument or may be provided as separate components, which can beelectrically attachable to the surgical instrument.

One form of the present surgical apparatus is particularly configuredfor disposable use by virtue of its straightforward construction.However, it is also contemplated that other forms of the presentsurgical instrument can be configured for non-disposable or multipleuses. Detachable connection of the present surgical instrument with anassociated oscillator and signal generator unit is presently disclosedfor single-patient use for illustrative purposes only. However,non-detachable integrated connection of the present surgical instrumentwith an associated oscillator and/or signal generator unit is alsocontemplated. Accordingly, various forms of the presently describedsurgical instruments may be configured for single use and/or multipleuse with either detachable and/or non-detachable integral oscillatorand/or signal generator unit, without limitation, and all combinationsof such configurations are contemplated to be within the scope of thepresent disclosure.

The surgical instruments disclosed herein are related to surgicalinstruments described in the following commonly owned applications andfiled Jun. 9, 2016: U.S. patent application Ser. No. 15/177,439, titled“Surgical System With User Adaptable Techniques” by Stulen et al., U.S.patent application Ser. No. 15/177,449, titled “Surgical System WithUser Adaptable Techniques Employing Multiple Energy Modalities Based OnTissue Parameters” by Wiener et al., U.S. patent application Ser. No.15/177,456, titled “Surgical System With User Adaptable Techniques BasedOn Tissue Impedance” by Yates et al., and U.S. patent application Ser.No. 15/177,466, titled “Surgical System With User Adaptable TechniquesEmploying Simultaneous Energy Modalities Based On Tissue Parameters” byYates et al., each of which is incorporated herein by reference in itsentirety.

With reference to FIGS. 1-5, one form of a surgical system 10 includingan ultrasonic surgical instrument is illustrated. FIG. 1 illustrates oneform of a surgical system 100 comprising a generator 102 and varioussurgical instruments 104, 106, 108 usable therewith. FIG. 2 is a diagramof the ultrasonic surgical instrument 104 of FIG. 1.

FIG. 1 illustrates a generator 102 configured to drive multiple surgicalinstruments 104, 106, 108. The first surgical instrument 104 comprises ahandpiece 105, an ultrasonic transducer 120, a shaft 126, and an endeffector 122. The end effector 122 comprises an ultrasonic blade 128acoustically coupled to the transducer 120 and a clamp arm 140. Thehandpiece 105 comprises a trigger 143 to operate the clamp arm 140 and acombination of the toggle buttons 134 a, 134 b, 134 c to energize anddrive the ultrasonic blade 128 or other function. The toggle buttons 134a, 134 b, 134 c can be configured to energize the ultrasonic transducer120 with the generator 102.

Still with reference to FIG. 1, the generator 102 also is configured todrive a second surgical instrument 106. The second surgical instrument106 is an RF electrosurgical instrument and comprises a handpiece 107, ashaft 127, and an end effector 124. The end effector 124 compriseselectrodes in the clamp arms143 and return through the ultrasonic blade149. The electrodes are coupled to and energized by a bipolar energysource within the generator 102. The handpiece 107 comprises a trigger147 to operate the clamp arm 145 and an energy button 135 to actuate anenergy switch to energize the electrodes in the end effector 124.

Still with reference to FIG. 1, the generator 102 also is configures todrive a combination electrosurgical and ultrasonic instrument 108. Thecombination electrosurgical and ultrasonic multifunction surgicalinstrument 108 comprises a handpiece 109, a shaft 129, and an endeffector 125. The end effector comprises an ultrasonic blade 149 and aclamp arm 145. The ultrasonic blade 149 is acoustically coupled to theultrasonic transducer 120. The handpiece 109 comprises a trigger 147 tooperate the clamp arm 145 and a combination of the toggle buttons 137 a,137 b, 137 c to energize and drive the ultrasonic blade 149 or otherfunction. The toggle buttons 137 a, 137 b, 137 c can be configured toenergize the ultrasonic transducer 120 with the generator 102 andenergize the ultrasonic blade 149 with a bipolar energy source alsocontained within the generator 102.

With reference to both FIGS. 1 and 2, the generator 102 is configurablefor use with a variety of surgical devices. According to various forms,the generator 102 may be configurable for use with different surgicaldevices of different types including, for example, the ultrasonicsurgical instrument 104, the electrosurgical or RF surgical devices,such as, the RF electrosurgical instrument 106, and the multifunctionsurgical instrument 108 that integrate electrosurgical RF and ultrasonicenergies delivered simultaneously from the generator 102.

Although in the form of FIG. 1, the generator 102 is shown separate fromthe surgical instruments 104, 106, 108, in one form, the generator 102may be formed integrally with either of the surgical instrument 104,106, 108 to form a unitary surgical system. The generator 102 comprisesan input device 110 located on a front panel of the generator 102console. The input device 110 may comprise any suitable device thatgenerates signals suitable for programming the operation of thegenerator 102. The generator 102 also may comprise one or more outputdevices 112.

The generator 102 is coupled to an ultrasonic transducer 120 via a cable144. The ultrasonic transducer 120 and a waveguide extending through ashaft 126 (waveguide not shown in FIG. 2) may collectively form anultrasonic drive system driving an ultrasonic blade 128 of an endeffector 122. The end effector 122 further may comprise a clamp arm 140to clamp tissue between the clamp arm 140 and the ultrasonic blade 128.In one form, the generator 102 may be configured to produce a drivesignal of a particular voltage, current, and/or frequency output signalthat can be stepped or otherwise modified with high resolution,accuracy, and repeatability.

Still with reference to FIG. 2, It will be appreciated that a surgicalinstrument 104 may comprise any combination of the toggle buttons 134 a,134 b, 134 c. For example, the surgical instrument 104 could beconfigured to have only two toggle buttons: a toggle button 134 a forproducing maximum ultrasonic energy output and a toggle button 134 c forproducing a pulsed output at either the maximum or less than maximumpower level. In this way, the drive signal output configuration of thegenerator 102 could be 5 continuous signals and 5 or 4 or 3 or 2 or 1pulsed signals. In certain forms, the specific drive signalconfiguration may be controlled based upon, for example, EEPROM settingsin the generator 102 and/or user power level selection(s).

In certain forms, a two-position switch may be provided as analternative to a toggle button 134 c. For example, a surgical instrument104 may include a toggle button 134 a for producing a continuous outputat a maximum power level and a two-position toggle button 134 b. In afirst detented position, toggle button 134 b may produce a continuousoutput at a less than maximum power level, and in a second detentedposition the toggle button 134 b may produce a pulsed output (e.g., ateither a maximum or less than maximum power level, depending upon theEEPROM settings).

Still with reference to FIG. 2, forms of the generator 102 may enablecommunication with instrument-based data circuits. For example, thegenerator 102 may be configured to communicate with a first data circuit136 and/or a second data circuit 138. For example, the first datacircuit 136 may indicate a burn-in frequency slope, as described herein.Additionally or alternatively, any type of information may becommunicated to second data circuit for storage therein via a datacircuit interface (e.g., using a logic device). Such information maycomprise, for example, an updated number of operations in which theinstrument has been used and/or dates and/or times of its usage. Incertain forms, the second data circuit may transmit data acquired by oneor more sensors (e.g., an instrument-based temperature sensor). Incertain forms, the second data circuit may receive data from thegenerator 102 and provide an indication to a user (e.g., an LEDindication or other visible indication) based on the received data. Thesecond data circuit 138 contained in the multifunction surgicalinstrument 108 of a surgical device. In some forms, the second datacircuit 138 may be implemented in a many similar to that of the firstdata circuit 136 described herein. An instrument interface circuit maycomprise a second data circuit interface to enable this communication.In one form, the second data circuit interface may comprise a tri-statedigital interface, although other interfaces also may be used. Incertain forms, the second data circuit may generally be any circuit fortransmitting and/or receiving data. In one form, for example, the seconddata circuit may store information pertaining to the particular surgicalinstrument with which it is associated. Such information may include,for example, a model number, a serial number, a number of operations inwhich the surgical instrument has been used, and/or any other type ofinformation. In some forms, the second data circuit 138 may storeinformation about the electrical and/or ultrasonic properties of anassociated transducer 120, end effector 122, or ultrasonic drive system.Various processes and techniques described herein may be executed by agenerator. It will be appreciated, however, that in certain exampleforms, all or a part of these processes and techniques may be performedby internal logic 139 of the multifunction surgical instrument 108.

FIG. 3 is a diagram of the surgical system 100 of FIG. 1. In variousforms, the generator 102 may comprise several separate functionalelements, such as modules and/or blocks. Different functional elementsor modules may be configured for driving the different kinds of surgicalinstruments 104, 106, 108. For example, an ultrasonic generator drivecircuit 114 may drive ultrasonic devices such as the ultrasonic surgicalinstrument 104 via a cable 142. An electrosurgery/RF generator drivecircuit 116 may drive the electrosurgical instrument 106 via a cable144. For example, the respective drive circuits 114, 116 may generaterespective drive signals for driving the surgical instruments 104, 106,108. In various forms, the ultrasonic generator drive circuit 114 (e.g.,ultrasonic drive circuit) and/or the electrosurgery/RF generator drivecircuit 116 (e.g., RF drive circuit) each may be formed integrally withthe generator 102. Alternatively, one or more of the drive circuits 114,116 may be provided as a separate circuit module electrically coupled tothe generator 102. (The drive circuits 114 and 116 are shown in phantomto illustrate this option.) Also, in some forms, the electrosurgery/RFgenerator drive circuit 116 may be formed integrally with the ultrasonicgenerator drive circuit 114, or vice versa. Also, in some forms, thegenerator 102 may be omitted entirely and the drive circuits 114, 116may be executed by processors or other hardware within the respectivesurgical instruments 104, 106, 108.

In other forms, the electrical outputs of the ultrasonic generator drivecircuit 114 and the electrosurgery/RF generator drive circuit 116 may becombined into a single drive circuit to provide a single electricalsignal capable of driving the multifunction surgical instrument 108simultaneously with electrosurgical RF and ultrasonic energies via acable 146. The multifunction surgical instrument 108 comprises anultrasonic transducer 120 coupled to an ultrasonic blade 149 and one ormore electrodes in the end effector 124 to receive electrosurgical RFenergy. In such implementations, the combined RF/ultrasonic signal iscoupled to the multifunction surgical instrument 108. The multifunctionsurgical instrument 108 comprises signal processing components to splitthe combined RF/ultrasonic signal such that the RF signal can bedelivered to the electrodes in the end effector 124 and the ultrasonicsignal can be delivered to the ultrasonic transducer 120.

In accordance with the described forms, the ultrasonic generator drivecircuit 114 may produce a drive signal or signals of particularvoltages, currents, and frequencies, e.g., 55,500 cycles per second(Hz). The drive signal or signals may be provided to the ultrasonicsurgical instrument 104, and specifically to the transducer 120, whichmay operate, for example, as described herein. The transducer 120 and awaveguide extending through the shaft 126 (waveguide not shown in FIG.2) may collectively form an ultrasonic drive system driving anultrasonic blade 128 of an end effector 122. In one form, the generator102 may be configured to produce a drive signal of a particular voltage,current, and/or frequency output signal that can be stepped or otherwisemodified with high resolution, accuracy, and repeatability.

The generator 102 may be activated to provide the drive signal to thetransducer 120 in any suitable manner. For example, the generator 102may comprise a foot switch 130 coupled to the generator 102 via a footswitch cable 132. A clinician may activate the transducer 120 bydepressing the foot switch 130. In addition, or instead of the footswitch 130 some forms of the ultrasonic surgical instrument 104 mayutilize one or more switches positioned on the hand piece that, whenactivated, may cause the generator 102 to activate the transducer 120.In one form, for example, the one or more switches may comprise a pairof toggle buttons 134 a, 134 b (FIG. 2), for example, to determine anoperating mode of the surgical instrument 104. When the toggle button134 a is depressed, for example, the ultrasonic generator 102 mayprovide a maximum drive signal to the transducer 120, causing it toproduce maximum ultrasonic energy output. Depressing toggle button 134 bmay cause the ultrasonic generator 102 to provide a user-selectabledrive signal to the transducer 120, causing it to produce less than themaximum ultrasonic energy output. The surgical instrument 104additionally or alternatively may comprise a second switch (not shown)to, for example, indicate a position of a jaw closure trigger foroperating jaws of the end effector 122. Also, in some forms, theultrasonic generator 102 may be activated based on the position of thejaw closure trigger, (e.g., as the clinician depresses the jaw closuretrigger to close the jaws, ultrasonic energy may be applied).

Additionally or alternatively, the one or more switches may comprises atoggle button 134 c that, when depressed, causes the generator 102 toprovide a pulsed output. The pulses may be provided at any suitablefrequency and grouping, for example. In certain forms, the power levelof the pulses may be the power levels associated with toggle buttons 134a, 134 b (maximum, less than maximum), for example.

In accordance with the described forms, the electrosurgery/RF generatordrive circuit 116 may generate a drive signal or signals with outputpower sufficient to perform bipolar electrosurgery using radio frequency(RF) energy. In bipolar electrosurgery applications, the drive signalmay be provided, for example, to electrodes of the electrosurgicalinstrument 106, for example. Accordingly, the generator 102 may beconfigured for therapeutic purposes by applying electrical energy to thetissue sufficient for treating the tissue (e.g., coagulation,cauterization, tissue welding).

The generator 102 may comprise an input device 110 (FIG. 1) located, forexample, on a front panel of the generator 102 console. The input device110 may comprise any suitable device that generates signals suitable forprogramming the operation of the generator 102. In operation, the usercan program or otherwise control operation of the generator 102 usingthe input device 110. The input device 110 may comprise any suitabledevice that generates signals that can be used by the generator (e.g.,by one or more processors contained in the generator) to control theoperation of the generator 102 (e.g., operation of the ultrasonicgenerator drive circuit 114 and/or electrosurgery/RF generator drivecircuit 116). In various forms, the input device 110 includes one ormore of buttons, switches, thumbwheels, keyboard, keypad, touch screenmonitor, pointing device, remote connection to a general purpose ordedicated computer. In other forms, the input device 110 may comprise asuitable user interface, such as one or more user interface screensdisplayed on a touch screen monitor, for example. Accordingly, by way ofthe input device 110, the user can set or program various operatingparameters of the generator, such as, for example, current (I), voltage(V), frequency (f), and/or period (T) of a drive signal or signalsgenerated by the ultrasonic generator drive circuit 114 and/orelectrosurgery/RF generator drive circuit 116.

The generator 102 also may comprise an output device 112 (FIGS. 1, 3),such as an output indicator, located, for example, on a front panel ofthe generator 102 console. The output device 112 includes one or moredevices for providing a sensory feedback to a user. Such devices maycomprise, for example, visual feedback devices (e.g., a visual feedbackdevice may comprise incandescent lamps, light emitting diodes (LEDs),graphical user interface, display, analog indicator, digital indicator,bar graph display, digital alphanumeric display, LCD display screen, LEDindicators), audio feedback devices (e.g., an audio feedback device maycomprise speaker, buzzer, audible, computer generated tone, computerizedspeech, voice user interface (VUI) to interact with computers through avoice/speech platform), or tactile feedback devices (e.g., a tactilefeedback device comprises any type of vibratory feedback, hapticactuator).

Although certain modules, circuits, and/or blocks of the generator 102may be described by way of example, it can be appreciated that a greateror lesser number of modules, circuits, and/or blocks may be used andstill fall within the scope of the forms. Further, although variousforms may be described in terms of modules, circuits, and/or blocks tofacilitate description, such modules, circuits, and/or blocks may beimplemented by one or more hardware components, e.g., processors,Digital Signal Processors (DSPs), Programmable Logic Devices (PLDs),Application Specific Integrated Circuits (ASICs), circuits, registersand/or software components, e.g., programs, subroutines, logic and/orcombinations of hardware and software components. Also, in some forms,the various modules described herein may be implemented utilizingsimilar hardware positioned within the surgical instruments 104, 106,108 (i.e., the generator 102 may be omitted).

In one form, the ultrasonic generator drive circuit 114 andelectrosurgery/RF drive circuit 116 may comprise one or more embeddedapplications implemented as firmware, software, hardware, or anycombination thereof. The drive circuits 114, 116 may comprise variousexecutable modules such as software, programs, data, drivers,application program interfaces (APIs), and so forth. The firmware may bestored in nonvolatile memory (NVM), such as in bit-masked read-onlymemory (ROM) or flash memory. In various implementations, storing thefirmware in ROM may preserve flash memory. The NVM may comprise othertypes of memory including, for example, programmable ROM (PROM),erasable programmable ROM (EPROM), electrically erasable programmableROM (EEPROM), or battery backed random-access memory (RAM) such asdynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), and/or synchronousDRAM (SDRAM).

In one form, the drive circuits 114, 116 comprise a hardware componentimplemented as a processor for executing program instructions formonitoring various measurable characteristics of the surgicalinstruments 104, 106, 108 and generating a corresponding output controlsignals for operating the surgical instruments 104, 106, 108. In formsin which the generator 102 is used in conjunction with the surgicalinstrument 104, the output control signal may drive the ultrasonictransducer 120 in cutting and/or coagulation operating modes.

Electrical characteristics of the surgical instrument 104 and/or tissuemay be measured and used to control operational aspects of the generator102 and/or provided as feedback to the user. In forms in which thegenerator 102 is used in conjunction with the electrosurgical instrument106, the output control signal may supply electrical energy (e.g., RFenergy) to the end effector 124 in cutting, coagulation and/ordesiccation modes. Electrical characteristics of the electrosurgicalinstrument 106 and/or tissue may be measured and used to controloperational aspects of the generator 102 and/or provide feedback to theuser. In various forms, as previously discussed, the hardware componentmay be implemented as a DSP, PLD, ASIC, circuits, and/or registers. Inone form, the processor may be configured to store and execute computersoftware program instructions to generate the output signal functionsfor driving various components of the surgical instruments 104, 106,108, such as the ultrasonic transducer 120 and the end effectors 122,124.

FIG. 4 illustrates an equivalent circuit 150 of an ultrasonictransducer, such as the ultrasonic transducer 120 shown in FIGS. 1-3,according to one form. The circuit 150 comprises a first “motional”branch having a serially connected inductance L_(s), resistance R_(s)and capacitance C_(s) that define the electromechanical properties ofthe resonator, and a second capacitive branch having a staticcapacitance C_(o). Drive current I_(g) may be received from a generatorat a drive voltage V_(g), with motional current I_(m) flowing throughthe first branch and current I_(g)-I_(m) flowing through the capacitivebranch. Control of the electromechanical properties of the ultrasonictransducer may be achieved by suitably controlling I_(g) and V_(g). Asexplained above, conventional generator architectures may include atuning inductor L_(t) (shown in phantom in FIG. 4) for tuning out in aparallel resonance circuit the static capacitance Co at a resonantfrequency so that substantially all of generator's current output I_(g)flows through the motional branch. In this way, control of the motionalbranch current I_(m) is achieved by controlling the generator currentoutput I_(g). The tuning inductor L_(t) is specific to the staticcapacitance C_(o) of an ultrasonic transducer, however, and a differentultrasonic transducer having a different static capacitance requires adifferent tuning inductor L_(t). Moreover, because the tuning inductorL_(t) is matched to the nominal value of the static capacitance Co at aresonant frequency, accurate control of the motional branch currentI_(m) is assured only at that frequency, and as frequency shifts downwith transducer temperature, accurate control of the motional branchcurrent is compromised.

Forms of the generator 102 shown in FIGS. 1-3 do not rely on a tuninginductor L_(t) to monitor the motional branch current I_(m). Instead,the generator 102 may use the measured value of the static capacitanceC_(o) in between applications of power for a specific ultrasonicsurgical instrument 104 (along with drive signal voltage and currentfeedback data) to determine values of the motional branch current I_(m)on a dynamic and ongoing basis (e.g., in real-time). Such forms of thegenerator 102 are therefore able to provide virtual tuning to simulate asystem that is tuned or resonant with any value of static capacitanceC_(o) at any frequency, and not just at the resonant frequency dictatedby a nominal value of the static capacitance C_(o).

FIG. 5 is a simplified block diagram of a generator 200 which is oneform of the generator 102 shown in FIGS. 1-3 for proving inductorlesstuning as described herein, among other benefits. Additional details ofthe generator 102 are described in commonly assigned U.S. patentapplication Ser. No. 12/896,360, titled “Surgical Generator ForUltrasonic And Electrosurgical Devices,” now U.S. Pat. No. 9,060,775,the disclosure of which is incorporated herein by reference in itsentirety. With reference to FIG. 5, the generator 200 may comprise apatient isolated stage 202 in communication with a non-isolated stage204 via a power transformer 206. A secondary winding 208 of the powertransformer 206 is contained in the isolated stage 202 and may comprisea tapped configuration (e.g., a center-tapped or a non-center-tappedconfiguration) to define drive signal outputs 210 a, 210 b, 210 c foroutputting drive signals to different surgical devices, such as, forexample, an ultrasonic surgical instrument 104 and an electrosurgicalinstrument 106 (as shown in FIGS. 1-3). In particular, the drive signaloutputs 210 a, 210 c may output an ultrasonic drive signal (e.g., a 420VRMS drive signal) to an ultrasonic surgical instrument 104, and thedrive signal outputs 210 b, 210 c may output an electrosurgical RF drivesignal (e.g., a 100V RMS drive signal) to an electrosurgical instrument106, with the output 210 b corresponding to the center tap of the powertransformer 206.

In certain forms, the ultrasonic and electrosurgical drive signals maybe provided simultaneously to distinct surgical instruments and/or to asingle surgical instrument having the capability to deliver bothultrasonic and electrosurgical energy to tissue, such as multifunctionsurgical instrument 108 (FIGS. 1 and 3). It will be appreciated that theelectrosurgical signal, provided either to a dedicated electrosurgicalinstrument and/or to a combined multifunction ultrasonic/electrosurgicalinstrument may be either a therapeutic or sub-therapeutic level signal.For example, the ultrasonic and radio frequency signals can be deliveredseparately or simultaneously from a generator with a single output portin order to provide the desired output signal to the surgicalinstrument, as will be discussed in more detail below. Accordingly, thegenerator can combine the ultrasonic and electrosurgical RF energies anddeliver the combined energies to the multifunctionultrasonic/electrosurgical instrument. Bipolar electrodes can be placedon one or both jaws of the end effector. One jaw may be driven byultrasonic energy in addition to electrosurgical RF energy, workingsimultaneously. The ultrasonic energy may be employed to dissect tissuewhile the electrosurgical RF energy may be employed for vessel sealing.

The non-isolated stage 204 may comprise a power amplifier 212 having anoutput connected to a primary winding 214 of the power transformer 206.In certain forms the power amplifier 212 may be comprise a push-pullamplifier. For example, the non-isolated stage 204 may further comprisea logic device 216 for supplying a digital output to a digital-to-analogconverter (DAC) 218, which in turn supplies a corresponding analogsignal to an input of the power amplifier 212. In certain forms thelogic device 216 may comprise a programmable gate array (PGA), afield-programmable gate array (FPGA), programmable logic device (PLD),among other logic circuits, for example. The logic device 216, by virtueof controlling the input of the power amplifier 212 via the DAC 218, maytherefore control any of a number of parameters (e.g., frequency,waveform shape, waveform amplitude) of drive signals appearing at thedrive signal outputs 210 a, 210 b, 210 c. In certain forms and asdiscussed below, the logic device 216, in conjunction with a processor(e.g., a digital signal processor discussed below), may implement anumber of digital signal processing (DSP)-based and/or other controltechniques to control parameters of the drive signals output by thegenerator 200.

Power may be supplied to a power rail of the power amplifier 212 by aswitch-mode regulator 220. In certain forms the switch-mode regulator220 may comprise an adjustable buck regulator, for example. Thenon-isolated stage 204 may further comprise a first processor such asDSP processor 222, which in one form may comprise a DSP processor suchas an Analog Devices ADSP-21469 SHARC DSP, available from AnalogDevices, Norwood, Mass., for example, although in various forms anysuitable processor may be employed. In certain forms the DSP processor222 may control operation of the switch-mode power converter 220responsive to voltage feedback data received from the power amplifier212 by the DSP processor 222 via an analog-to-digital converter (ADC)224. In one form, for example, the DSP processor 222 may receive asinput, via the ADC 224, the waveform envelope of a signal (e.g., an RFsignal) being amplified by the power amplifier 212. The DSP processor222 may then control the switch-mode regulator 220 (e.g., via apulse-width modulated (PWM) output) such that the rail voltage suppliedto the power amplifier 212 tracks the waveform envelope of the amplifiedsignal. By dynamically modulating the rail voltage of the poweramplifier 212 based on the waveform envelope, the efficiency of thepower amplifier 212 may be significantly improved relative to a fixedrail voltage amplifier schemes.

In certain forms, the logic device 216, in conjunction with the DSPprocessor 222, may implement a direct digital synthesizer (DDS) controlscheme to control the waveform shape, frequency and/or amplitude ofdrive signals output by the generator 200. In one form, for example, thelogic device 216 may implement a DDS control technique by recallingwaveform samples stored in a dynamically-updated look-up table (LUT),such as a RAM LUT, which may be embedded in an FPGA. This controltechnique is particularly useful for ultrasonic applications in which anultrasonic transducer, such as the ultrasonic transducer 120 (FIGS.1-3), may be driven by a clean sinusoidal current at its resonantfrequency. Because other frequencies may excite parasitic resonances,minimizing or reducing the total distortion of the motional branchcurrent may correspondingly minimize or reduce undesirable resonanceeffects. Because the waveform shape of a drive signal output by thegenerator 200 is impacted by various sources of distortion present inthe output drive circuit (e.g., the power transformer 206, the poweramplifier 212), voltage and current feedback data based on the drivesignal may be input into a technique, such as an error control techniqueimplemented by the DSP processor 222, which compensates for distortionby suitably pre-distorting or modifying the waveform samples stored inthe LUT on a dynamic, ongoing basis (e.g., in real-time). In one form,the amount or degree of pre-distortion applied to the LUT samples may bebased on the error between a computed motional branch current and adesired current waveform shape, with the error being determined on asample-by-sample basis. In this way, the pre-distorted LUT samples, whenprocessed through the drive circuit, may result in a motional branchdrive signal having the desired waveform shape (e.g., sinusoidal) foroptimally driving the ultrasonic transducer. In such forms, the LUTwaveform samples will therefore not represent the desired waveform shapeof the drive signal, but rather the waveform shape that is required toultimately produce the desired waveform shape of the motional branchdrive signal when distortion effects are taken into account.

The non-isolated stage 204 may further comprise an ADC 226 and an ADC228 coupled to the output of the power transformer 206 via respectiveisolation transformers 230, 232 for respectively sampling the voltageand current of drive signals output by the generator 200. In certainforms, the ADCs 226, 228 may be configured to sample at high speeds(e.g., 80 MSPS) to enable oversampling of the drive signals. In oneform, for example, the sampling speed of the ADCs 226, 228 may enableapproximately 200× (depending on frequency) oversampling of the drivesignals. In certain forms, the sampling operations of the ADC 226, 228may be performed by a singe ADC receiving input voltage and currentsignals via a two-way multiplexer. The use of high-speed sampling informs of the generator 200 may enable, among other things, calculationof the complex current flowing through the motional branch (which may beused in certain forms to implement DDS-based waveform shape controldescribed herein), accurate digital filtering of the sampled signals,and calculation of real power consumption with a high degree ofprecision. Voltage and current feedback data output by the ADCs 226, 228may be received and processed (e.g., FIFO buffering, multiplexing) bythe logic device 216 and stored in data memory for subsequent retrievalby, for example, the DSP processor 222. As noted above, voltage andcurrent feedback data may be used as input to a technique forpre-distorting or modifying LUT waveform samples on a dynamic andongoing basis. In certain forms, this may require each stored voltageand current feedback data pair to be indexed based on, or otherwiseassociated with, a corresponding LUT sample that was output by the logicdevice 216 when the voltage and current feedback data pair was acquired.Synchronization of the LUT samples and the voltage and current feedbackdata in this manner contributes to the correct timing and stability ofthe pre-distortion technique.

In certain forms, the voltage and current feedback data may be used tocontrol the frequency and/or amplitude (e.g., current amplitude) of thedrive signals. In one form, for example, voltage and current feedbackdata may be used to determine impedance phase. The frequency of thedrive signal may then be controlled to minimize or reduce the differencebetween the determined impedance phase and an impedance phase setpoint(e.g., 00), thereby minimizing or reducing the effects of ultrasonicdistortion and correspondingly enhancing impedance phase measurementaccuracy. The determination of phase impedance and a frequency controlsignal may be implemented in the DSP processor 222, for example, withthe frequency control signal being supplied as input to a DDS controltechnique implemented by the logic device 216.

In another form, for example, the current feedback data may be monitoredin order to maintain the current amplitude of the drive signal at acurrent amplitude setpoint. The current amplitude setpoint may bespecified directly or determined indirectly based on specified voltageamplitude and power setpoints. In certain forms, control of the currentamplitude may be implemented by control technique, such as, for example,a PID control technique, in the DSP processor 222. Variables controlledby the control technique to suitably control the current amplitude ofthe drive signal may include, for example, the scaling of the LUTwaveform samples stored in the logic device 216 and/or the full-scaleoutput voltage of the DAC 218 (which supplies the input to the poweramplifier 212) via a DAC 234.

The non-isolated stage 204 may further comprise a second processor suchas UI processor 236 for providing, among other things user interface(UI) functionality. In one form, the UI processor 236 may comprise anAtmel AT91SAM9263 processor having an ARM 926EJ-S core, available fromAtmel Corporation, San Jose, Calif., for example. Examples of UIfunctionality supported by the UI processor 236 may include audible andvisual user feedback, communication with peripheral devices (e.g., via aUniversal Serial Bus (USB) interface), communication with the footswitch 130, communication with an input device 118 (e.g., a touch screendisplay) and communication with an output device 112 (e.g., a speaker),as shown in FIG. 3, for example. The UI processor 236 may communicatewith the DSP processor 222 and the logic device 216 (e.g., via serialperipheral interface (SPI) buses). Although the UI processor 236 mayprimarily support UI functionality, it also may coordinate with the DSPprocessor 222 to implement hazard mitigation in certain forms. Forexample, the UI processor 236 may be programmed to monitor variousaspects of user input and/or other inputs (e.g., touch screen inputs,foot switch 130 inputs (FIG. 3), temperature sensor inputs) and maydisable the drive output of the generator 200 when an erroneouscondition is detected.

In certain forms, both the DSP processor 222 and the UI processor 236,for example, may determine and monitor the operating state of thegenerator 200. For the DSP processor 222, the operating state of thegenerator 200 may dictate, for example, which control and/or diagnosticprocesses are implemented by the DSP processor 222. For the UI processor236, the operating state of the generator 200 may dictate, for example,which elements of a user interface (e.g., display screens, sounds) arepresented to a user. The respective DSP and UI processors 222, 236 mayindependently maintain the current operating state of the generator 200and recognize and evaluate possible transitions out of the currentoperating state. The DSP processor 222 may function as the master inthis relationship and determine when transitions between operatingstates are to occur. The UI processor 236 may be aware of validtransitions between operating states and may confirm if a particulartransition is appropriate. For example, when the DSP processor 222instructs the UI processor 236 to transition to a specific state, the UIprocessor 236 may verify that requested transition is valid. In theevent that a requested transition between states is determined to beinvalid by the UI processor 236, the UI processor 236 may cause thegenerator 200 to enter a failure mode.

The non-isolated stage 204 may further comprise a controller 238 formonitoring input devices 110 (e.g., a capacitive touch sensor used forturning the generator 200 on and off, a capacitive touch screen, e.g.,as shown in FIGS. 1 and 3). In certain forms, the controller 238 maycomprise at least one processor and/or other controller device incommunication with the UI processor 236. In one form, for example, thecontroller 238 may comprise a processor (e.g., a Mega168 8-bitcontroller available from Atmel) configured to monitor user inputprovided via one or more capacitive touch sensors. In one form, thecontroller 238 may comprise a touch screen controller (e.g., a QT5480touch screen controller available from Atmel) to control and manage theacquisition of touch data from a capacitive touch screen.

In certain forms, when the generator 200 is in a “power off” state, thecontroller 238 may continue to receive operating power (e.g., via a linefrom a power supply of the generator 200. In this way, the controller238 may continue to monitor an input device 110 (e.g., a capacitivetouch sensor located on a front panel of the generator 200) for turningthe generator 200 on and off. When the generator 200 is in the power offstate, the controller 238 may wake the power supply (e.g., enableoperation of one or more DC/DC voltage converters of the power supply)if activation of the “on/off” input device 110 by a user is detected.The controller 238 may therefore initiate a sequence for transitioningthe generator 200 to a “power on” state. Conversely, the controller 238may initiate a sequence for transitioning the generator 200 to the poweroff state if activation of the “on/off” input device 110 is detectedwhen the generator 200 is in the power on state. In certain forms, forexample, the controller 238 may report activation of the “on/off” inputdevice 110 to the UI processor 236, which in turn implements thenecessary process sequence for transitioning the generator 200 to thepower off state. In such forms, the controller 238 may have noindependent ability for causing the removal of power from the generator200 after its power on state has been established.

In certain forms, the controller 238 may cause the generator 200 toprovide audible or other sensory feedback for alerting the user that apower on or power off sequence has been initiated. Such an alert may beprovided at the beginning of a power on or power off sequence and priorto the commencement of other processes associated with the sequence.

In certain forms, the isolated stage 202 may comprise an instrumentinterface circuit 240 to, for example, provide a communication interfacebetween a control circuit of a surgical device (e.g., a control circuitcomprising hand piece switches) and components of the non-isolated stage204, such as, for example, the programmable logic device 216, the DSPprocessor 222 and/or the UI processor 236. The instrument interfacecircuit 240 may exchange information with components of the non-isolatedstage 204 via a communication link that maintains a suitable degree ofelectrical isolation between the stages 202, 204, such as, for example,an infrared (IR)-based communication link. Power may be supplied to theinstrument interface circuit 240 using, for example, a low-dropoutvoltage regulator powered by an isolation transformer driven from thenon-isolated stage 204.

In one form, the instrument interface circuit 240 may comprise a logicdevice 242 (e.g., logic circuit, programmable logic circuit, PGA, FPGA,PLD) in communication with a signal conditioning circuit 242. The signalconditioning circuit 244 may be configured to receive a periodic signalfrom the logic circuit 242 (e.g., a 2 kHz square wave) to generate abipolar interrogation signal having an identical frequency. Theinterrogation signal may be generated, for example, using a bipolarcurrent source fed by a differential amplifier. The interrogation signalmay be communicated to a surgical device control circuit (e.g., by usinga conductive pair in a cable that connects the generator 200 to thesurgical device) and monitored to determine a state or configuration ofthe control circuit. The control circuit may comprise a number ofswitches, resistors and/or diodes to modify one or more characteristics(e.g., amplitude, rectification) of the interrogation signal such that astate or configuration of the control circuit is uniquely discernablebased on the one or more characteristics. In one form, for example, thesignal conditioning circuit 244 may comprises an ADC for generatingsamples of a voltage signal appearing across inputs of the controlcircuit resulting from passage of interrogation signal therethrough. Thelogic device 242 (or a component of the non-isolated stage 204) may thendetermine the state or configuration of the control circuit based on theADC samples.

In one form, the instrument interface circuit 240 may comprise a firstdata circuit interface 246 to enable information exchange between thelogic circuit 242 (or other element of the instrument interface circuit240) and a first data circuit disposed in or otherwise associated with asurgical device. In certain forms, for example, a first data circuit 136(FIG. 2) may be disposed in a cable integrally attached to a surgicaldevice hand piece, or in an adaptor for interfacing a specific surgicaldevice type or model with the generator 200. The first data circuit 136may be implemented in any suitable manner and may communicate with thegenerator according to any suitable protocol including, for example, asdescribed herein with respect to the first circuit 136. In certainforms, the first data circuit may comprise a non-volatile storagedevice, such as an electrically erasable programmable read-only memory(EEPROM) device. In certain forms and referring again to FIG. 5, thefirst data circuit interface 246 may be implemented separately from thelogic device 242 and comprise suitable circuitry (e.g., discrete logicdevices, a processor) to enable communication between the programmablelogic device 242 and the first data circuit. In other forms, the firstdata circuit interface 246 may be integral with the logic device 242.

In certain forms, the first data circuit 136 (FIG. 2) may storeinformation pertaining to the particular surgical device with which itis associated. Such information may include, for example, a modelnumber, a serial number, a number of operations in which the surgicaldevice has been used, and/or any other type of information. Thisinformation may be read by the instrument interface circuit 1098 (e.g.,by the logic device 242), transferred to a component of the non-isolatedstage 204 (e.g., to logic device 216, DSP processor 222 and/or UIprocessor 236) for presentation to a user via an output device 112(FIGS. 1 and 3) and/or for controlling a function or operation of thegenerator 200. Additionally, any type of information may be communicatedto first data circuit 136 for storage therein via the first data circuitinterface 246 (e.g., using the logic device 242). Such information maycomprise, for example, an updated number of operations in which thesurgical device has been used and/or dates and/or times of its usage.

As discussed previously, a surgical instrument may be detachable from ahand piece (e.g., as shown in FIGS. 1 and 2, the transducer 120 and theshaft 126 is detachable from the handpiece 105 of the ultrasonicsurgical instrument 104) to promote instrument interchangeability and/ordisposability. In such cases, conventional generators may be limited intheir ability to recognize particular instrument configurations beingused and to optimize control and diagnostic processes accordingly. Theaddition of readable data circuits to surgical device instruments toaddress this issue is problematic from a compatibility standpoint,however. For example, designing a surgical device to remain backwardlycompatible with generators that lack the requisite data readingfunctionality may be impractical due to, for example, differing signalschemes, design complexity, and cost. Forms of instruments discussedherein address these concerns by using data circuits that may beimplemented in existing surgical instruments economically and withminimal design changes to preserve compatibility of the surgical deviceswith current generator platforms.

With reference to FIGS. 1-3 and 5, additionally, forms of the generator200 may enable communication with instrument-based data circuits. Forexample, the generator 200 may be configured to communicate with asecond data circuit 138 contained in the ultrasonic surgical instrument104 (e.g., and/or the other surgical instruments 106, 108). In someforms, the second data circuit 138 may be implemented in a many similarto that of the first data circuit 136 described herein. The instrumentinterface circuit 240 may comprise a second data circuit interface 248to enable this communication. In one form, the second data circuitinterface 248 may comprise a tri-state digital interface, although otherinterfaces also may be used. In certain forms, the second data circuitmay generally be any circuit for transmitting and/or receiving data. Inone form, for example, the second data circuit may store informationpertaining to the particular surgical instrument with which it isassociated. Such information may include, for example, a model number, aserial number, a number of operations in which the surgical instrumenthas been used, and/or any other type of information. In some forms, thesecond data circuit 138 may store information about the electricaland/or ultrasonic properties of an associated transducer 120, endeffector 122, or ultrasonic drive system. For example, the first datacircuit 136 may indicate a burn-in frequency slope, as described herein.Additionally or alternatively, any type of information may becommunicated to second data circuit for storage therein via the seconddata circuit interface 248 (e.g., using the logic device 242). Suchinformation may comprise, for example, an updated number of operationsin which the instrument has been used and/or dates and/or times of itsusage. In certain forms, the second data circuit may transmit dataacquired by one or more sensors (e.g., an instrument-based temperaturesensor). In certain forms, the second data circuit may receive data fromthe generator 200 and provide an indication to a user (e.g., an LEDindication or other visible indication) based on the received data.

In certain forms, the second data circuit and the second data circuitinterface 248 may be configured such that communication between thelogic device 242 and the second data circuit can be effected without theneed to provide additional conductors for this purpose (e.g., dedicatedconductors of a cable connecting a hand piece to the generator 200). Inone form, for example, information may be communicated to and from thesecond data circuit using a 1-wire bus communication scheme implementedon existing cabling, such as one of the conductors used transmitinterrogation signals from the signal conditioning circuit 244 to acontrol circuit in a hand piece. In this way, design changes ormodifications to the surgical device that might otherwise be necessaryare minimized or reduced. Moreover, because different types ofcommunications implemented over a common physical channel can befrequency-band separated, the presence of a second data circuit may be“invisible” to generators that do not have the requisite data readingfunctionality, thus enabling backward compatibility of the surgicaldevice instrument.

In certain forms, the isolated stage 202 may comprise at least oneblocking capacitor 250-1 connected to the drive signal output 210 b toprevent passage of DC current to a patient. A single blocking capacitormay be required to comply with medical regulations or standards, forexample. While failure in single-capacitor designs is relativelyuncommon, such failure may nonetheless have negative consequences. Inone form, a second blocking capacitor 250-2 may be provided in serieswith the blocking capacitor 250-1, with current leakage from a pointbetween the blocking capacitors 250-1, 250-2 being monitored by, forexample, an ADC 252 for sampling a voltage induced by leakage current.The samples may be received by the logic device 242, for example. Basedchanges in the leakage current (as indicated by the voltage samples inthe form of FIG. 5), the generator 200 may determine when at least oneof the blocking capacitors 250-1, 250-2 has failed. Accordingly, theform of FIG. 5 provides a benefit over single-capacitor designs having asingle point of failure.

In certain forms, the non-isolated stage 204 may comprise a power supply254 for outputting DC power at a suitable voltage and current. The powersupply may comprise, for example, a 400 W power supply for outputting a48 VDC system voltage. The power supply 254 may further comprise one ormore DC/DC voltage converters 256 for receiving the output of the powersupply to generate DC outputs at the voltages and currents required bythe various components of the generator 200. As discussed above inconnection with the controller 238, one or more of the DC/DC voltageconverters 256 may receive an input from the controller 238 whenactivation of the “on/off” input device 110 (FIG. 3) by a user isdetected by the controller 238 to enable operation of, or wake, theDC/DC voltage converters 256.

With reference back to FIG. 1, having described operational details ofvarious forms of the surgical system 100 operations for the abovesurgical system 100 may be further described generally in terms of aprocess for cutting and coagulating tissue employing a surgicalinstrument comprising an input device 110 and the generator 102.Although a particular process is described in connection with theoperational details, it can be appreciated that the process merelyprovides an example of how the general functionality described hereincan be implemented by the surgical system 100. Further, the givenprocess does not necessarily have to be executed in the order presentedherein unless otherwise indicated. As previously discussed, the inputdevices 110 may be employed to program the output (e.g., impedance,current, voltage, frequency) of the surgical instruments 104, 106, 108.

FIG. 6 illustrates a generator 300 comprising one form of drive system302, according to one aspect of the present disclosure. The generator300 is similar to the generators 102, 200 described in connection within FIGS. 1 and 5. The generator 300 produces an ultrasonic electricalsignal for driving an ultrasonic transducer, also referred to as a drivesignal. The drive system 302 is flexible and can create an ultrasonicelectrical output drive signal 304 at a desired frequency and powerlevel setting for driving an ultrasonic transducer 306. In variousforms, the generator 300 may comprise several separate functionalelements, such as modules and/or blocks. Although certain modules,circuits, and/or blocks may be described by way of example, it can beappreciated that a greater or lesser number of modules, circuits, and/orblocks may be used and still fall within the scope of the forms.Further, although various forms may be described in terms of modules,circuits, and/or blocks to facilitate description, such modules,circuits, and/or blocks may be implemented by one or more hardwarecomponents, e.g., processors, Digital Signal Processors (DSPs),Programmable Logic Devices (PLDs), Application Specific IntegratedCircuits (ASICs), circuits, registers and/or software components, e.g.,programs, subroutines, logic and/or combinations of hardware andsoftware components.

In one form, the drive system 302 of the generator 300 may comprise oneor more embedded applications implemented as firmware, software,hardware, or any combination thereof. The drive system 302 may comprisevarious executable modules such as software, programs, data, drivers,application program interfaces (APIs), and so forth. The firmware may bestored in nonvolatile memory (NVM), such as in bit-masked read-onlymemory (ROM) or flash memory. In various implementations, storing thefirmware in ROM may preserve flash memory. The NVM may comprise othertypes of memory including, for example, programmable ROM (PROM),erasable programmable ROM (EPROM), electrically erasable programmableROM (EEPROM), or battery backed random-access memory (RAM) such asdynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), and/or synchronousDRAM (SDRAM).

In one form, the drive system 302 comprises a hardware componentimplemented as a processor 308 for executing program instructions formonitoring various measurable characteristics of the ultrasonic surgicalinstrument 104 (FIG. 1) and generating various functions as an outputsignal for driving the ultrasonic transducer 306 in cutting and/orcoagulation operating modes. It will be appreciated by those skilled inthe art that the generator 300 and the drive system 302 may compriseadditional or fewer components and only a simplified version of thegenerator 300 and the drive system 302 are described herein forconciseness and clarity. In various forms, as previously discussed, thehardware component may be implemented as a DSP, PLD, ASIC, circuits,and/or registers. In one form, the processor 308 may be configured tostore and execute computer software program instructions to generate theoutput signal functions for driving various components of the ultrasonicsurgical instrument 104 (FIG. 1), such as an ultrasonic transducer 306,an end effector, and/or a blade 340.

In one form, under control of one or more software program routines, theprocessor 308 executes the methods in accordance with the describedforms to generate a function formed by a stepwise waveform of drivesignals comprising current (I), voltage (V), and/or frequency (f) forvarious time intervals or periods (T). The stepwise waveforms of thedrive signals may be generated by forming a piecewise linear combinationof constant functions over a plurality of time intervals created byvarying the generator 300 drive signals, e.g., output drive current (I),voltage (V), and/or frequency (f). The time intervals or periods (T) maybe predetermined (e.g., fixed and/or programmed by the user) or may bevariable. Variable time intervals may be defined by setting the drivesignal to a first value and maintaining the drive signal at that valueuntil a change is detected in a monitored characteristic. Examples ofmonitored characteristics may comprise, for example, transducerimpedance, tissue impedance, tissue heating, tissue transection, tissuecoagulation, and the like. The ultrasonic drive signals generated by thegenerator 300 include, without limitation, ultrasonic drive signalscapable of exciting the ultrasonic transducer 306 in various vibratorymodes such as, for example, the primary longitudinal mode and harmonicsthereof as well flexural and torsional vibratory modes.

In one form, the executable modules comprise one or more technique(s)310 stored in memory that when executed causes the processor 308 togenerate a function formed by a stepwise waveform of drive signalscomprising current (I), voltage (V), and/or frequency (f) for varioustime intervals or periods (T). The stepwise waveforms of the drivesignals may be generated by forming a piecewise linear combination ofconstant functions over two or more time intervals created by varyingthe generator 300 output drive current (I), voltage (V), and/orfrequency (f). The drive signals may be generated either forpredetermined fixed time intervals or periods (T) of time or variabletime intervals or periods of time in accordance with the one or moretechnique(s) 310. Under control of the processor 308, the generator 300varies (e.g., increment or decrement over time) the current (I), voltage(V), and/or frequency (f) up or down at a particular resolution for apredetermined period (T) or until a predetermined condition is detected,such as a change in a monitored characteristic (e.g., transducerimpedance, tissue impedance). The steps can change in programmedincrements or decrements. If other steps are desired, the generator 300can increase or decrease the step adaptively based on measured systemcharacteristics.

In operation, the user can program the operation of the generator 300using the input device 312 located on the front panel of the generator300 console. The input device 312 may comprise any suitable device thatgenerates signals 314 that can be applied to the processor 308 tocontrol the operation of the generator 300. In various forms, the inputdevice 312 includes buttons, switches, thumbwheels, keyboard, keypad,touch screen monitor, pointing device, remote connection to a generalpurpose or dedicated computer. In other forms, the input device 312 maycomprise a suitable user interface. Accordingly, by way of the inputdevice 312, the user can set or program the current (I), voltage (V),frequency (f), and/or period (T) for programming the output function ofthe generator 300. The processor 308 then displays the selected powerlevel by sending a signal on line 316 to an output indicator 318.

In various forms, the output indicator 318 may provide visual, audible,and/or tactile feedback to the surgeon to indicate the status of asurgical procedure, such as, for example, when tissue cutting andcoagulating is complete based on a measured characteristic of theultrasonic surgical instrument 104 (FIG. 1), e.g., transducer impedance,tissue impedance, or other measurements as subsequently described. Byway of example, and not limitation, visual feedback comprises any typeof visual indication device including incandescent lamps or lightemitting diodes (LEDs), graphical user interface, display, analogindicator, digital indicator, bar graph display, digital alphanumericdisplay. By way of example, and not limitation, audible feedbackcomprises any type of buzzer, computer generated tone, computerizedspeech, voice user interface (VUI) to interact with computers through avoice/speech platform. By way of example, and not limitation, tactilefeedback comprises any type of vibratory feedback provided through aninstrument housing handle assembly.

In one form, the processor 308 may be configured or programmed togenerate a digital current drive signal 320 and a digital frequencysignal 322. These drive signals 320, 322 are applied to a direct digitalsynthesizer (DDS) circuit 324 to adjust the amplitude and the frequency(f) of the output drive signal 304 to the ultrasonic transducer 306. Theoutput of the DDS circuit 324 is applied to an amplifier 326 whoseoutput is applied to a transformer 328. The output of the transformer328 is the output drive signal 304 applied to the ultrasonic transducer306, which is coupled to the blade 340 by way of a waveguide.

In one form, the generator 300 comprises one or more measurement modulesor components that may be configured to monitor measurablecharacteristics of the ultrasonic surgical instrument 104 (FIG. 1). Inthe illustrated form, the processor 308 may be employed to monitor andcalculate system characteristics. As shown, the processor 308 measuresthe impedance Z of the ultrasonic transducer 306 by monitoring thecurrent supplied to the transducer 306 and the voltage applied to theultrasonic transducer 306. In one form, a current sense circuit 330 isemployed to sense the current supplied to the ultrasonic transducer 306and a voltage sense circuit 332 is employed to sense the output voltageapplied to the ultrasonic transducer 306. These signals may be appliedto the analog-to-digital converter 336 (ADC) via an analog multiplexer334 circuit or switching circuit arrangement. The analog multiplexer 334routes the appropriate analog signal to the ADC 336 for conversion. Inother forms, multiple ADCs 336 may be employed for each measuredcharacteristic instead of the multiplexer 334 circuit. The processor 308receives the digital output 338 of the ADC 336 and calculates thetransducer impedance Z based on the measured values of current andvoltage. The processor 308 adjusts the output drive signal 304 such thatit can generate a desired power versus load curve. In accordance withprogrammed techniques 310, the processor 308 can vary the drive signal320, e.g., the current or frequency, in any suitable increment ordecrement in response to the transducer impedance Z.

Having described operational details of various forms of the surgicalsystem 100 shown in FIG. 1, operations for the above surgical system 100may be further described in terms of a process for cutting andcoagulating a blood vessel employing a surgical instrument comprisingthe input device 110 and the transducer impedance measurementcapabilities of the drive system 302 described with reference to FIG. 6.Although a particular process is described in connection with theoperational details, it can be appreciated that the process merelyprovides an example of how the general functionality described hereincan be implemented by the surgical system 100. Further, the givenprocess does not necessarily have to be executed in the order presentedherein unless otherwise indicated.

FIG. 7 illustrates one aspect of a drive system of a generator 400comprising a tissue impedance module 442. The drive system 402 generatesthe ultrasonic electrical drive signal 404 to drive the ultrasonictransducer 406. In one aspect, the tissue impedance module 442 may beconfigured to measure the impedance Zt of tissue grasped between theblade 440 and the clamp arm assembly 444. The tissue impedance module442 comprises an RF oscillator 446, a voltage sensing circuit 448, and acurrent sensing circuit 450. The voltage and current sensing circuits448, 450 respond to the RF voltage Vrf applied to the blade 440electrode and the RF current irf flowing through the blade 440electrode, the tissue, and the conductive portion of the clamp armassembly 444. The sensed current Irf and the sensed voltage Vrf from thecurrent sense circuit 430 and the voltage sense circuit 432 areconverted to digital form by the ADC 436 via the analog multiplexer 434.The processor 408 receives the digitized output 438 of the ADC 436 anddetermines the tissue impedance Zt by calculating the ratio of the RFvoltage Vrf to current Irf measured by the voltage sensing circuit 448and the current sense circuit 450.

In one form, the processor 408 may be configured or programmed togenerate a digital current signal 420 and a digital frequency signal422. These signals 420, 422 are applied to a direct digital synthesizer(DDS) circuit 424 to adjust the amplitude and the frequency (f) of thecurrent output signal 404 to the transducer 406. The output of the DDScircuit 424 is applied to an amplifier 426 whose output is applied to atransformer 428. The output of the transformer 428 is the signal 404applied to the ultrasonic transducer 406, which is coupled to the blade440 by way of a waveguide.

In one aspect, the transection of the inner muscle layer and the tissuemay be detected by sensing the tissue impedance Zt. Accordingly,detection of the tissue impedance Zt may be integrated with an automatedprocess for separating the inner muscle layer from the outer adventitialayer prior to transecting the tissue without causing a significantamount of heating, which normally occurs at resonance.

In one form, the RF voltage Vrf applied to the blade 440 electrode andthe RF current Irf flowing through the blade 440 electrode, the tissue,and the conductive portion of the clamp arm assembly 444 are suitablefor vessel sealing and//or dissecting. Thus, the RF power output of thegenerator 400 can be selected for non-therapeutic functions such astissue impedance measurements as well as therapeutic functions such asvessel sealing and/or dissection. It will be appreciated, that in thecontext of the present disclosure, the ultrasonic and the RFelectrosurgical energies can be supplied by the generator eitherindividually or simultaneously.

In operation, the user can program the operation of the generator 400using the input device 412 located on the front panel of the generator400 console. The input device 412 may comprise any suitable device thatgenerates signals 414 that can be applied to the processor 408 tocontrol the operation of the generator 400. In various forms, the inputdevice 412 includes buttons, switches, thumbwheels, keyboard, keypad,touch screen monitor, pointing device, remote connection to a generalpurpose or dedicated computer. In other forms, the input device 412 maycomprise a suitable user interface. Accordingly, by way of the inputdevice 412, the user can set or program the current (I), voltage (V),frequency (f), and/or period (T) for programming the function output ofthe generator 400. The processor 408 then displays the selected powerlevel by sending a signal on line 416 to an output indicator 418.

In various forms, feedback is provided by the output indicator 418. Theoutput indicator 418 is particularly useful in applications where thetissue being manipulated by the end effector is out of the user's fieldof view and the user cannot see when a change of state occurs in thetissue. The output indicator 418 communicates to the user that a changein tissue state has occurred. As previously discussed, the outputindicator 418 may be configured to provide various types of feedback tothe user including, without limitation, visual, audible, and/or tactilefeedback to indicate to the user (e.g., surgeon, clinician) that thetissue has undergone a change of state or condition of the tissue. Byway of example, and not limitation, as previously discussed, visualfeedback comprises any type of visual indication device includingincandescent lamps or LEDs, graphical user interface, display, analogindicator, digital indicator, bar graph display, digital alphanumericdisplay. By way of example, and not limitation, audible feedbackcomprises any type of buzzer, computer generated tone, computerizedspeech, VUI to interact with computers through a voice/speech platform.By way of example, and not limitation, tactile feedback comprises anytype of vibratory feedback provided through the instrument housinghandle assembly. The change of state of the tissue may be determinedbased on transducer and tissue impedance measurements as previouslydescribed, or based on voltage, current, and frequency measurements.

In one form, the various executable modules (e.g., algorithms 410)comprising computer readable instructions can be executed by theprocessor 408 portion of the generator 400. In various forms, theoperations described with respect to the techniques may be implementedas one or more software components, e.g., programs, subroutines, logic;one or more hardware components, e.g., processors, DSPs, PLDs, ASICs,circuits, registers; and/or combinations of software and hardware. Inone form, the executable instructions to perform the techniques may bestored in memory. When executed, the instructions cause the processor408 to determine a change in tissue state provide feedback to the userby way of the output indicator 418. In accordance with such executableinstructions, the processor 408 monitors and evaluates the voltage,current, and/or frequency signal samples available from the generator400 and according to the evaluation of such signal samples determineswhether a change in tissue state has occurred. As further describedbelow, a change in tissue state may be determined based on the type ofultrasonic instrument and the power level that the instrument isenergized at. In response to the feedback, the operational mode of theultrasonic surgical instrument may be controlled by the user or may beautomatically or semi-automatically controlled.

As noted above, a single output generator can deliver both RF andultrasonic energy through a single port and these signals can bedelivered separately or simultaneously to the end effector to treattissue. A single output port generator can include a single outputtransformer with multiple taps to provide power, either RF or ultrasonicenergy, to the end effector depending on the type of treatment of tissuebeing performed. For example, the generator can deliver energy withhigher voltage and lower current to drive an ultrasonic transducer, withlower voltage and higher current as required to drive electrodes forsealing tissue, or with a coagulation waveform for spot coagulationusing either monopolar or bipolar electrosurgical electrodes. The outputwaveform from the generator can be steered, switched, or filtered toprovide the desired frequency to the end effector of the surgicalinstrument.

FIG. 8 illustrates an example of a generator 500 for delivering multipleenergy modalities to a surgical instrument. The generator 500 is similarto the generator 102 described in connection with FIG. 1 and includesfunctionalities of the generators 200, 300, 400 shown in FIGS. 5-7. Forconciseness and clarity of disclosure, hereinbelow, the various logicflow diagrams are described in connection with the generator 500, whichis a high level block diagram representation. Accordingly, the reader isdirected to the description of the functional blocks of the generators200, 300, 400 in FIGS. 5-7 for additional details that may be necessaryto understand and practice the logic flow diagrams described hereinbelowin connection with the generator 500.

Turning back to FIG. 8, the generator 500 provides radio frequency andultrasonic signals for delivering energy to a surgical instrument. Theradio frequency and ultrasonic signals may be provided alone or incombination and may be provided simultaneously. As noted above, at leastone generator output can deliver multiple energy modalities (e.g.,ultrasonic, bipolar or monopolar RF, irreversible and/or reversibleelectroporation, and/or microwave energy, among others) through a singleport and these signals can be delivered separately or simultaneously tothe end effector to treat tissue. The generator 500 comprises aprocessor 502 coupled to a waveform generator 504. The processor 502 andwaveform generator 504 are configured to generate a variety of signalwaveforms based on information stored in a memory coupled to theprocessor 502, not shown for clarity of disclosure. The digitalinformation associated with a waveform is provided to the waveformgenerator 504 which includes one or more digital-to-analog (DAC)converters to convert the digital input into an analog output. Theanalog output is fed to an amplifier 1106 for signal conditioning andamplification. The conditioned and amplified output of the amplifier 506is coupled to a power transformer 508. The signals are coupled acrossthe power transformer 508 to the secondary side, which is in the patientisolation side. A first signal of a first energy modality is provided tothe surgical instrument between the terminals labeled ENERGY1 andRETURN. A second signal of a second energy modality is coupled across acapacitor 510 and is provided to the surgical instrument between theterminals labeled ENERGY2 and RETURN. It will be appreciated that morethan two energy modalities may be output and thus the subscript “n” maybe used to designate that up to n ENERGYn terminals may be provided,where n is a positive integer greater than 1. It also will beappreciated that up to “n” return paths RETURNn may be provided withoutdeparting from the scope of the present disclosure.

A first voltage sensing circuit 512 is coupled across the terminalslabeled ENERGY1 and the RETURN path to measure the output voltagetherebetween. A second voltage sensing circuit 524 is coupled across theterminals labeled ENERGY2 and the RETURN path to measure the outputvoltage therebetween. A current sensing circuit 514 is disposed inseries with the RETURN leg of the secondary side of the powertransformer 508 as shown to measure the output current for either energymodality. If different return paths are provided for each energymodality, then a separate current sensing circuit should be provided ineach return leg. The outputs of the first and second voltage sensingcircuits 512, 524 are provided to respective isolation transformers 516,522 and the output of the current sensing circuit 514 is provided toanother isolation transformer 518. The outputs of the isolationtransformers 516, 518, 522 in the on the primary side of the powertransformer 508 (non-patient-isolated side) are provided to a one ormore analog-to-digital converters 526 (ADC). The digitized output of theADC 526 is provided to the processor 502 for further processing andcomputation. The output voltages and output current feedback informationcan be employed to adjust the output voltage and current provided to thesurgical instrument and to compute output impedance, among otherparameters. Input/output communications between the processor 502 andpatient isolated circuits is provided through an interface circuit 520.Sensors also may be in electrical communication with the processor 502by way of the interface 520.

In one aspect, the impedance may be determined by the processor 502 bydividing the output of either the first voltage sensing circuit 512coupled across the terminals labeled ENERGY1/RETURN or the secondvoltage sensing circuit 524 coupled across the terminals labeledENERGY2/RETURN by the output of the current sensing circuit 514 disposedin series with the RETURN leg of the secondary side of the powertransformer 508. The outputs of the first and second voltage sensingcircuits 512, 524 are provided to separate isolations transformers 516,522 and the output of the current sensing circuit 514 is provided toanother isolation transformer 516. The digitized voltage and currentsensing measurements from the ADC 526 are provided the processor 502 forcomputing impedance. As an example, the first energy modality ENERGY1may be ultrasonic energy and the second energy modality ENERGY2 may beRF energy. Nevertheless, in addition to ultrasonic and bipolar ormonopolar RF energy modalities, other energy modalities includeirreversible and/or reversible electroporation and/or microwave energy,among others. Also, although the example illustrated in FIG. 8 shows asingle return path RETURN may be provided for two or more energymodalities, in other aspects multiple return paths RETURNn may beprovided for each energy modality ENERGYn. Thus, as described herein,the ultrasonic transducer impedance may be measured by dividing theoutput of the first voltage sensing circuit 512 by the current sensingcircuit 514 and the tissue impedance may be measured by dividing theoutput of the second voltage sensing circuit 524 by the current sensingcircuit 514.

As shown in FIG. 8, the generator 500 comprising at least one outputport can include a power transformer 508 with a single output and withmultiple taps to provide power in the form of one or more energymodalities, such as ultrasonic, bipolar or monopolar RF, irreversibleand/or reversible electroporation, and/or microwave energy, amongothers, for example, to the end effector depending on the type oftreatment of tissue being performed. For example, the generator 500 candeliver energy with higher voltage and lower current to drive anultrasonic transducer, with lower voltage and higher current to drive RFelectrodes for sealing tissue, or with a coagulation waveform for spotcoagulation using either monopolar or bipolar RF electrosurgicalelectrodes. The output waveform from the generator 500 can be steered,switched, or filtered to provide the frequency to the end effector ofthe surgical instrument. The connection of an ultrasonic transducer tothe generator 500 output would be preferably located between the outputlabeled ENERGY1 and RETURN as shown in FIG. 8. An In one example, aconnection of RF bipolar electrodes to the generator 500 output would bepreferably located between the output labeled ENERGY2 and RETURN. In thecase of monopolar output, the preferred connections would be activeelectrode (e.g., pencil or other probe) to the ENERGY2 output and asuitable return pad connected to the RETURN output.

In other aspects, the generators 102, 200, 300, 400, 500 described inconnection with FIGS. 1-3 and 5-8, the ultrasonic generator drivecircuit 114, and/or electrosurgery/RF drive circuit 116 as described inconnection with FIG. 3 may be formed integrally with any one of thesurgical instruments 104, 106, 108 described in connection with FIGS. 1and 2. Accordingly, any of the processors, digital signal processors,circuits, controllers, logic devices, ADCs, DACs, amplifiers,converters, transformers, signal conditioners, data interface circuits,current and voltage sensing circuits, direct digital synthesis circuits,multiplexer (analog or digital), waveform generators, RF generators,memory, and the like, described in connection with any one of thegenerators 102, 200, 300, 400, 500 can be located within the surgicalinstruments 104, 106, 108 or may be located remotely from the surgicalinstruments 104, 106, 108 and coupled to the surgical instruments viawired and/or wireless electrical connections.

Examples of waveforms representing energy for delivery from a generatorare illustrated in FIGS. 9-13. FIG. 9 illustrates an example graph 600showing first and second individual waveforms representing an RF outputsignal 602 and an ultrasonic output signal 604 superimposed on the sametime and voltage scale for comparison purposes. These output signals602, 604 are provided at the ENERGY output of the generator 500 shown inFIG. 8. Time (t) is shown along the horizontal axis and voltage (V) isshown along the vertical axis. The RF output signal 602 has a frequencyof about 330 kHz RF and a peak-to-peak voltage of ±1V. The ultrasonicoutput signal 604 has a frequency of about 55 kHz and a peak-to-peakvoltage of ±1V. It will be appreciated that the time (t) scale along thehorizontal axis and the voltage (V) scale along the vertical axis arenormalized for comparison purposes and may be different actualimplementations, or represent other electrical parameters such ascurrent.

FIG. 10 illustrates an example graph 610 showing the sum of the twooutput signals 602, 604 shown in FIG. 9. Time (t) is shown along thehorizontal axis and voltage (V) is shown along the vertical axis. Thesum of the RF output signal 602 and the ultrasonic output signal 604shown in FIG. 9 produces a combined output signal 612 having a 2Vpeak-to-peak voltage, which is twice the amplitude of the original RFand ultrasonic signals shown (1V peak-to-peak) shown in FIG. 9. Anamplitude of twice the original amplitude can cause problems with theoutput section of the generator, such as distortion, saturation,clipping of the output, or stresses on the output components. Thus, themanagement of a single combined output signal 612 that has multipletreatment components is an important aspect of the generator 500 shownin FIG. 8. There are a variety of ways to achieve this management. Inone form, one of the two RF or ultrasonic output signals 602, 604 can bedependent on the peaks of the other output signal.

For example, FIG. 11 illustrates an example graph 620 showing a combinedoutput signal 622 representative of a dependent sum of the outputsignals 602, 604 shown in FIG. 9. Time (t) is shown along the horizontalaxis and voltage (V) is shown along the vertical axis. As shown in FIG.11, the RF output signal 602 component of FIG. 9 depends on the peaks ofthe ultrasonic output signal 604 component of FIG. 9 such that theamplitude of the RF output signal component of the dependent sumcombined output signal 622 is reduced when an ultrasonic peak isanticipated. As shown in the example graph 620 in FIG. 11, the peakshave been reduced from 2 to 1.5. In another form, one of the outputsignals is a function of the other output signal.

For example, FIG. 11 illustrates an example graph 630 showing an outputsignal 632 representative of a dependent sum of the output signals 602,604 shown in FIG. 9. Time (t) is shown along the horizontal axis andvoltage (V) is shown along the vertical axis. As shown in FIG. 12, theRF output signal is a function of the ultrasonic output signal. Thisprovides a hard limit on the amplitude of the output. As shown in FIG.12, the ultrasonic output signal is extractable as a sine wave while theRF output signal has distortion but not in a way to affect thecoagulation performance of the RF output signal.

A variety of other techniques can be used for compressing and/orlimiting the waveforms of the output signals. It should be noted thatthe integrity of the ultrasonic output signal 604 (FIG. 9) can be moreimportant than the integrity of the RF output signal 602 (FIG. 9) aslong as the RF output signal 602 has low frequency components for safepatient levels so as to avoid neuro-muscular stimulation. In anotherform, the frequency of an RF waveform can be changed on a continuousbasis in order to manage the peaks of the waveform. Waveform control isimportant as more complex RF waveforms, such as a coagulation-typewaveform 644, as illustrated in the graph 640 shown in FIG. 13, areimplemented with the system. Again, time (t) is shown along thehorizontal axis and voltage (V) is shown along the vertical axis.

FIGS. 14-42 (26-54) illustrate various configurations of sensors,circuits, and techniques for measuring tissue parameters to facilitateexecuting the various adaptive tissue identification and treatmenttechnique described herein. FIG. 14 illustrates one aspect of an endeffector 700 comprising RF data sensors 706, 708 a, 708 b located on theclamp arm 702. The end effector 700 comprises a clamp arm 702 and anultrasonic blade 704. The clamp arm 702 is shown clamping tissue 710located between the clamp arm 702 and the ultrasonic blade 704. A firstsensor 706 is located in a center portion of the clamp arm 702. Secondand third sensors 708 a, 708 b are located on lateral portions of theclamp arm 702. The sensors 706, 708 a, 708 b are mounted or formedintegrally with on a flexible circuit 712 (shown more particularly inFIG. 15 and more particularly segmented flexible circuits 800, 900 shownin FIGS. 17 and 18) configured to be fixedly mounted to the clamp arm702.

The end effector 700 is an example end effector for the multifunctionsurgical instrument 108 shown in FIGS. 1 and 2. The sensors 706, 708 a,708 b are electrically connected to an energy source, such as forexample, the generator 500 shown in FIG. 8. The sensors 706, 708 a, 708b are powered by suitable sources within the generator and the signalsgenerated by the sensors 706, 708 a, 708 b are provided to analog and/ordigital processing circuits of the generator 500.

In one aspect, the first sensor 706 is a force sensor to measure anormal force F₃ applied to the tissue 710 by the clamp arm 702. Thesecond and third sensors 708 a, 708 b include one or more elements toapply RF energy to the tissue 710, measure tissue impedance, down forceF₁, transverse forces F₂, and temperature, among other parameters.Electrodes 709 a, 709 b are electrically coupled to the generator andapply RF energy to the tissue 710. In one aspect, the first sensor 706and the second and third sensors 708 a, 708 b are strain gauges tomeasure force or force per unit area. It will be appreciated that themeasurements of the down force F₁, the lateral forces F₂, and the normalforce F₃ may be readily converted to pressure by determining the surfacearea upon which the force sensors 706, 708 a, 708 b are acting upon.Additionally, as described with particularity herein, the flexiblecircuit 712 may comprise temperature sensors embedded in one or morelayers of the flexible circuit 712. The one or more temperature sensorsmay be arranged symmetrically or asymmetrically and provide tissue 710temperature feedback to control circuits of the generator.

FIG. 15 illustrates one aspect of the flexible circuit 712 shown in FIG.14 in which the sensors 706, 708 a, 708 b may be mounted to or formedintegrally therewith. The flexible circuit 712 is configured to fixedlyattach to the clamp arm 702. As shown particularly in FIG. 15,asymmetric temperature sensors 714 a, 714 b are mounted to the flexiblecircuit 712 to enable measuring the temperature of the tissue 710 (FIG.14).

FIG. 16 is a cross-sectional view of the flexible circuit 712 shown inFIG. 15. The flexible circuit 712 comprises multiple layers and isfixedly attached to the clamp arm 702. A top layer of the flexiblecircuit 712 is an electrode 709 a, which is electrically coupled to anenergy source, such as the generators 102, 200, 300, 400, 500 (FIGS. 1-3and 4-8), to apply RF energy to the tissue 710 (FIG. 14). A layer ofelectrical insulation 718 is provided below the electrode 709 a layer toelectrically isolate the sensors 714 a, 706, 708 a from the electrode709 a. The temperature sensors 714 a are disposed below the layer ofelectrical insulation 718. The first force (pressure) sensor 706 islocated below the layer containing the temperature sensors 714 a andabove a compressive layer 720. The second force (pressure) sensor 708 ais located below the compressive layer 720 and above the clamp arm 702frame.

FIG. 17 illustrates one aspect of a segmented flexible circuit 800configured to fixedly attach to a clamp arm 804 of an end effector. Thesegmented flexible circuit 800 comprises a distal segment 802 a andlateral segments 802 b, 802 c that include individually addressablesensors to provide local tissue control, as described herein inconnection with FIGS. 14-16, for example. The segments 802 a, 802 b, 802c are individually addressable to treat tissue and to measure tissueparameters based on individual sensors located within each of thesegments 802 a, 802 b, 802 c. The segments 802 a, 802 b, 802 c of thesegmented flexible circuit 800 are mounted to the clamp arm 804 and areelectrically coupled to an energy source, such as the generators 102,200, 300, 400, 500 (FIGS. 1-3 and 4-8), via electrical conductiveelements 806. A Hall effect sensor 808, or any suitable magnetic sensor,is located on a distal end of the clamp arm 804. The Hall effect sensor808 operates in conjunction with a magnet to provide a measurement of anaperture defined by the clamp arm 804, which otherwise may be referredto as a tissue gap, as shown with particularity in FIG. 19.

FIG. 18 illustrates one aspect of a segmented flexible circuit 900configured to mount to a clamp arm 904 of an end effector. The segmentedflexible circuit 1900 comprises a distal segment 902 a and lateralsegments 902 b, 902 c that include individually addressable sensors fortissue control, as described herein in connection with FIGS. 14-17, forexample. The segments 902 a, 902 b, 902 c are individually addressableto treat tissue and to read individual sensors located within each ofthe segments 902 a, 902 b, 902 c. The segments 902 a, 902 b, 902 c ofthe segmented flexible circuit 900 are mounted to the clamp arm 904 andare electrically coupled to an energy source, such as the generators102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), via electrical conductiveelements 906. A Hall effect sensor 908, or other suitable magneticsensor, is provided on a distal end of the clamp arm 904. The Halleffect sensor 908 operates in conjunction with a magnet to provide ameasurement of an aperture defined by the clamp arm 904 of the endeffector or tissue gap as shown with particularity in FIG. 19. Inaddition, a plurality of lateral asymmetric temperature sensors 910 a,910 b are mounted on or formally integrally with the segmented flexiblecircuit 900 to provide tissue temperature feedback to control circuitsin the generator.

FIG. 19 illustrates one aspect of an end effector 1000 configured tomeasure a tissue gap G_(T). The end effector 1000 comprises a jaw member1002 and a clamp arm 904. The flexible circuit 900 as described in FIG.18, is mounted to the clamp arm 904. The flexible circuit 900 comprisesa Hall effect sensor 908 that operates with a magnet 1004 mounted to thejaw member 1002 to measure the tissue gap G_(T). This technique can beemployed to measure the aperture defined between the clamp arm 904 andthe jaw member 1002. The jaw member 1002 may be an ultrasonic blade.

FIG. 20 illustrates one aspect of a left-right segmented flexiblecircuit 1100. The left-right segmented flexible circuit 1100 comprises aplurality of segments L1-L5 on the left side of the left-right segmentedflexible circuit 1100 and a plurality of segments R1-R5 on the rightside of the left-right segmented flexible circuit 1100. Each of thesegments L1-L5 and R1-R5 comprise temperature sensors and force sensorsto sense tissue parameters locally within each segment L1-L5 and R1-R5.The left-right segmented flexible circuit 1100 are configured toinfluence the RF treatment energy based on tissue parameters sensedlocally within each of the segments L1-L5 and R1-R5.

FIG. 21 illustrates one aspect of an end effector 1200 comprisingsegmented flexible circuit 1100 as shown in FIG. 20. The end effector1200 comprises a clamp arm 1202 and an ultrasonic blade 1204. Thesegmented flexible circuit 1100 is mounted to the clamp arm 1202. Eachof the sensors disposed within the segments 1-5 are configured to detectthe presence of tissue positioned between the clamp arm 1202 and theultrasonic blade 1204 and represent tissue zones 1-5. In theconfiguration shown in FIG. 21, the end effector 1200 is shown in anopen position ready to receive or grasp tissue between the clamp arm1202 and the ultrasonic blade 1204.

FIG. 22 illustrates the end effector 1200 shown in FIG. 21 with theclamp arm 1202 clamping tissue 1206 between the clamp arm 1202 and theultrasonic blade 1204. As shown in FIG. 22, the tissue 1206 ispositioned between segments 1-3 and represents tissue zones 1-3.Accordingly, tissue 1206 is detected by the sensors in segments 1-3 andthe absence of tissue (empty) is detected in section 1208 by segments4-5. The information regarding the presence and absence of tissue 1206positioned within certain segments 1-3 and 4-5, respectively, iscommunicated to a control circuit of the generator, such as thegenerators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8). The generator500 is configured to energize only the segments 1-3 where tissue 1206 isdetected and does not energize the segments 4-5 where tissue is notdetected. It will be appreciated that the segments 1-5 may contain anysuitable temperature, force/pressure, and/or Hall effect magneticsensors to measure tissue parameters of tissue located within certainsegments 1-5 and electrodes to deliver RF energy to tissue located incertain segments 1-5.

FIG. 23 illustrates graphs 1300 of energy applied by the right and leftside of an end effector based on locally sensed tissue parameters. Asdiscussed herein, the clamp arm of an end effector may comprisetemperature sensors, force/pressure sensors, Hall effector sensors,among others, along the right and left sides of the clamp arm as shown,for example, in FIGS. 14-22. Thus, RF energy can be selectively appliedto tissue positioned between the clam jaw and the ultrasonic blade. Thetop graph 1302 depicts power P_(R) applied to a right side segment ofthe clamp arm versus time (t) based on locally sensed tissue parameters.Thus, the generator, such as the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), is configured to measure the sensed tissueparameters and to apply power P_(R) to a right side segment of the clamparm. The generator 500 delivers an initial power level P₁ to the tissuevia the right side segment and then decreases the power level to P₂based on local sensing of tissue parameters (e.g., temperature,force/pressure, thickness) in one or more segments. The bottom graph1304 depicts power P_(L) applied to a left side segment of the clamp armversus time (t) based on locally sensed tissue parameters. The generator500 delivers an initial power level of P₁ to the tissue via the leftside segment and then increases the power level to P₃ based localsensing of tissue parameters (e.g., temperature, force/pressure,thickness). As depicted in the bottom graph 1304, the generator isconfigured to re-adjust the energy delivered P₃ based on sensing oftissue parameters (e.g., temperature, force/pressure, thickness).

FIG. 24 illustrates a graph 1400 depicting one aspect of adjustment ofthreshold due to the measurement of a secondary tissue parameter such ascontinuity, temperature, pressure, and the like. The horizontal axis ofthe graph 1400 is time (t) and the vertical axis is tissue impedance(Z). The curve 1412 represents the change of tissue impedance (Z) overtime (t) as different energy modalities are applied to the tissue. Withreference also to FIGS. 20-22, the original threshold 1402 is appliedwhen tissue is detected in all five segments 1-5 (tissue zones 1-5) andthe adjusted threshold 1404 is applied when the tissue is detected intissue segments 1-3 (tissue zones 1-3). Accordingly, once the tissue islocated in particulars segments (zones) the control circuit in thegenerator adjusts the threshold accordingly.

As shown in FIG. 24, the curve 1412 includes three separate sections1406, 1408, 1410. The first section 1406 of the curve 1412 representsthe time when RF energy is applied to the tissue in tissue zones 1-3until the tissue impedance drops below the adjusted threshold 1404. Atthat point 1414, which may indicate that a tissue seal is completed, theenergy modality applied to tissue zones 1-3 is changed from RF energy toultrasonic energy. The ultrasonic energy is then applied in the secondand third sections 1408, 1410 and the impedance rises exponentiallyuntil the tissue is severed or cut.

FIG. 25 is a cross-sectional view of one aspect of a flexible circuit1500 comprising RF electrodes and data sensors embedded therein. Theflexible circuit 1500 can be mounted to the right or left portion of anRF clamp arm 1502, which is made of electrically conductive materialsuch as metal. Below the RF clamp arm 1502 down force/pressure sensors1506 a, 1506 b are embedded below a laminate layer 1504. A transverseforce/pressure sensor 1508 is located below the down force/pressuresensor 1506 a, 1506 b layer and a temperature sensor is 1510 is locatedbelow the transverse force/pressure sensor 1508. An electrode 1512electrically coupled to the generator and configured to apply RF energyto the tissue 1514 is located below the temperature sensor 1510.

FIG. 26 is a cross-sectional view of one aspect of an end effector 1600configured to sense force or pressure applied to tissue located betweena clamp arm and an ultrasonic blade. The end effector 1600 comprises aclamp jaw 1602 and a flexible circuit 1604 fixedly mounted to the clamparm 1602. The clamp arm 1602 applies forces F₁ and F₂ to the tissue 1606of variable density and thickness, which can be measure by first andsecond force/pressure sensors 1608, 1610 located in different layers ofthe flexible circuit 1604. A compressive layer 1612 is sandwichedbetween the first and second force/pressure sensors 1608, 1610. Anelectrode 1614 is located on outer portion of the flexible circuit 1604which contacts the tissue. As described herein, other layers of theflexible circuit 1604 may comprise additional sensors such temperaturesensors, thickness sensors, and the like.

FIGS. 27-29 illustrate various schematic diagrams of flexible circuitsof the signal layer, sensor wiring, and an RF energy drive circuit. FIG.27 is a schematic diagram of one aspect of a signal layer of a flexiblecircuit 1700. The flexible circuit 1700 comprises multiple layers (˜4 to˜6, for example). One layer will supply the integrated circuits withpower and another layer with ground. Two additional layers will carrythe RF power RF1 and RF2 separately. An analog multiplexer switch 1702has eight bidirectional translating switches that can be controlledthrough the I²C bus. The SCL/SDA upstream pair fans out to eightdownstream pairs, or channels. Any individual SCn/SDn channel orcombination of channels can be selected, determined by the contents of aprogrammable control register. The upstream pairs SCL/SDA are connectedto a control circuit in the generator. There are six down streamsensors, three on each side of the clamp arm. A first side 1704 acomprises a first thermocouple 1706 a, a first pressure sensor 1708 a,and a first Hall effect sensor 1710 a. A second side 1704 b comprises asecond thermocouple 1706 b, a second pressure sensor 1708 b, and asecond Hall effect sensor 1710 b. FIG. 28 is a schematic diagram 1750 ofsensor wiring for the flexible circuit 1700 shown in FIG. 27.

FIG. 29 is a schematic diagram of one aspect of an RF energy drivecircuit 1800. The RF energy drive circuit 1800 comprises an analogmultiplexer 1702 described in connection with FIG. 27. The analogmultiplexer multiplexes various signals from the upstream channelsSCL/SDA. A current sensor 1802 is coupled in series with the return orground leg of the power supply circuit to measure the current suppliedby the power supply. An FET temperature sensor 1804 provided the ambienttemperature. A pulse width modulation (PWM) watchdog timer 1808automatically generates a system reset if the main program neglects toperiodically service it. It is provided to automatically reset the RFenergy drive circuit 1800 when it hangs because of a software orhardware fault.

A drive circuit 1806 provides left and right RF energy outputs. Thedigital signal is provided to the SCL/SDA inputs of the analogmultiplexer 1702 from a control circuit of the generator. Adigital-to-analog converter (DAC) converts the digital input to ananalog output to drive a pulse width modulation (PWM) circuit 1812coupled to an oscillator 1814. The PWM circuit 1812 provides a firstgate drive signal 1816 a to a first transistor output stage 1818 a todrive a first RF (Left) energy output. The PWM circuit 1812 alsoprovides a second gate drive signal 1816 b to a second transistor outputstage 1818 to drive a second RF (Right) energy output.

The circuits 1700, 1750, 1800 described in connection with FIGS. 27-29are electrically coupled to the generators 200, 300, 400, 500 shown inFIGS. 5-7. For example, the circuits 1700, 1750, 1800 may be coupled tothe generator 200 via the signal conditioning circuit 244 and may becoupled to the generator 500 through the interface circuit 520.

FIG. 30 is a graphical representation 1900 of measuring tissue gap at apreset time. A first graph 1902 represents tissue impedance Z versustime (t) where the horizontal axis represents time (t) and the verticalaxis represents tissue impedance Z. A second graph 1904 representschange in tissue gap Δ_(gap) versus time(t) where the horizontal axisrepresents time (t) and the vertical axis represents change in tissuegap Δ_(gap). A third graph 1906 represents force F versus time (t) wherethe horizontal axis represents time (t) and the vertical axis representsforce F. With a constant force F applied to tissue and impedance Zinterrogation to define a wait period, energy modality (e.g., RF andultrasonic) and motor control parameters, displacement at a timeprovides velocity. With reference to the three graphs 1902, 1904, 1906,impedance sensing energy is applied during a first period 1908 todetermine the tissue type such as thin mesentery tissue (solid line),intermediate thickness vessel tissue (dashed line), or thickuterus/bowel tissue (dash-dot line).

As shown in the third graph 1906, the clamp arm initially applies aforce which ramps up from zero exponentially until it reaches a constantforce 1924. The preset time t₁ is selected such that it occurs some timeafter the clamp arm force reaches a constant force 1924. As shown in thefirst and second graphs 1902, 1904, from the time the clamp force isapplied to the mesentery tissue until the preset time t₁ is reached, thechange in tissue gap Δ_(gap) curve 1912 decreases exponentially and thetissue impedance curve 1918 also decreases until the preset time t₁ isreached. From the preset time t₁, a short delay 1928 is applied beforetreatment energy is applied to the mesentery tissue at t_(E1).

As shown in the first and second graphs 1902, 1904, from the time theclamp force is applied to the vessel tissue until the preset time t₁ isreached, the change in tissue gap Δ_(gap)curve 1916 also decreaseexponentially and the tissue impedance curve 1920 also decreases untilthe preset time t₁ is reached. From the preset time t₁, a medium delay1930 is applied before treatment energy is applied to the vessel tissueat t_(E2).

As shown in the first and second graphs 1902, 1904, from the time theclamp force is applied to the uterus/bowel tissue until the preset timet₁ is reached, the change in tissue gap Δ_(gap) curve 1914 dropsexponentially and the tissue impedance curve 1914 also drops until thepreset time t₁ is reached. From the preset time t₁, a short delay 1928is applied before treatment energy is applied to the mesentery tissue att_(E1).

FIG. 31 is a time to preset force 2008 versus time graph 2000 for thin,medium, and thick tissue types. The horizontal axis represents time (t)and the vertical axis represents force (F) applied by the clamp arm tothe tissue. The graph 2000 depicts three curves, one for thin tissue2002 shown in solid line, one for medium thickness tissue 2004 shown indash-dot line, and thick tissue 2006 in dashed line. The graph 2000depicts measuring time at a preset force as an alternative to tissue gapto control delayed energy mode and other control parameters.Accordingly, the time to preset force 2008 for thick tissue 2006 ist_(1a), the time to preset force 2008 for medium thickness tissue 2004is t_(1b), and the time to preset force 2008 for thin tissue 2002 ist_(1c).

Once the force reaches the preset force 2008, energy is applied to thetissue. For thin tissue 2002 the time to preset t_(1c)>0.5 seconds andthen RF energy is applied for an energizing period t_(e) of about 1-3seconds. For thick tissue 2006 the time to preset t_(1a)<0.5 seconds andthen RF energy is applied for an energizing period t_(e) of about 5-9seconds. For medium thickness tissue 2004 the time to preset t_(1b) isabout 0.5 seconds and then RF energy is applied for an energizing periodt_(e) of about 3 to 5 seconds.

FIG. 32 is a graphical depiction of a graph 2100 of three curves 2102,2104, 2106, where the first curve 2102 represents power (P),voltage(V_(RF)), and current (I_(RF)) versus tissue impedance (Z), thesecond curve 2104 and third curve 2106 represent tissue impedance (Z)versus time (t). The first curve 2102 illustrates the application ofpower (P) for thick tissue impedance range 2110 and thin tissueimpedance range 2112. As the tissue impedance Z increases, the currentI_(RF) decrease and the voltage V_(RF) increases. The power curve Pincreases until it reaches a maximum power output 2108 which coincideswith the intersection 2114 of the current I_(RF) and voltage V_(RF)curves.

The second curve 2104 represents the measured tissue impedance Z versustime (t). The tissue impedance threshold limit 2120 is the cross overlimit for switching between the RF and ultrasonic energy modalities. Forexample, as shown in FIG. 32, RF energy is applied while the tissueimpedance is above the tissue impedance threshold limit 2120 andultrasonic energy 2124 is applied while the tissue impedance is belowthe tissue impedance threshold limit 2120. Accordingly, with referenceback to the second curve 2104, the tissue impedance of the thin tissuecurve 2116 remains above the tissue impedance threshold limit 2120, thusonly RF energy modality is applied to the tissue. On the other hand, RFenergy modality is applied to the tick tissue while the impedance isabove the tissue impedance threshold limit 2120 and ultrasonic energy isapplied to the tissue when the impedance is below the tissue impedancethreshold limit 2120. Accordingly, the energy modality switches from RFto ultrasonic when the tissue impedance falls below the tissue impedancethreshold limit 2120 and the energy modality switches from ultrasonic toRF when the tissue impedance rises above the tissue impedance thresholdlimit 2120.

FIG. 33 is a plan view of one aspect of an end effector 2200. The endeffector 2200 comprises a clamp arm 2202 and a shaft 2204. The clamp arm2202 pivots about pivot point 2206 and defines a pivot angle. FIG. 34 isa side view of the end effector 2200 shown in FIG. 33 with a partial cutaway view to expose the underlying structure of the clamp arm 2202 andan ultrasonic blade 2208. An electrode 2210 is fixedly mounted to theclamp arm 2202. The electrode 2210 is electrically coupled to thegenerator and is configured to apply RF energy to tissue located betweenthe clamp arm 2202 and the ultrasonic blade 2208. FIG. 35 is partialsectional view of the end effector shown in FIGS. 33, 34 to expose theultrasonic blade and right and left electrodes 2210 a, 2210 b,respectively.

FIG. 36 is a cross-sectional view taken at section 36-36 of the endeffector 2200 shown in FIG. 33. The end effector 2200 comprises anultrasonic blade 2208 acoustically coupled to an ultrasonic transducerwhich is electrically driven by the generator. The clamp arm 2202comprises an electrode 2210 a on the right side and an electrode 2210 bon the left side (from the perspective of the operator). The right sideelectrode 2210 a defines a first width W₁ and defines a first gap G₁between the electrode 2210 a and the ultrasonic blade 2208. The leftside electrode 2210 b defines a second width W₂ and defines a second gapG₂ between the electrode 2210 b and the ultrasonic blade 2208. In oneaspect the first width W₁ is less than the second width W₂ and the firstgap G₁ is less than the second gap G₂. With reference also to FIG. 35, asoft polymeric pad 2212 is located between the ultrasonic blade 2208 andthe clamp arm 2202. A high density polymeric pad 2214 is locatedadjacent the soft polymeric pad 2212 to prevent the ultrasonic blade2208 from shorting the electrodes 2210 a, 2210 b. In one aspect, thesoft polymeric pads 2212, 2214 can be made of polymers known under thetradename TEFLON (polytetrafluoroethylene polymers and copolymers), forexample.

FIG. 37 is cross-sectional view taken at section 37-37 of the endeffector 2200 shown in FIG. 33. At the plane where section 37-37 the endeffector 2200 is thinner and has more curvature than section 36-36. Theright side electrode 2210 a defines a third width W₃ and defines a thirdgap G₃ between the electrode 2210 a and the ultrasonic blade 2208. Theleft side electrode 2210 b defines a fourth width W₄ and defines afourth gap G₄ between the electrode 2210 b and the ultrasonic blade2208. In one aspect the third width W₃ is less than the fourth width W₄and the third gap G₃ is less than the fourth gap G₄.

FIG. 38 is a cross-sectional view taken at section 36-36 of the endeffector 2200 shown in FIG. 33, except that the ultrasonic blade 2208′has a different geometric configuration. The end effector 2200′comprises an ultrasonic blade 2208′cacoustically coupled to anultrasonic transducer which is electrically driven by the generator. Theclamp arm 2202′ comprises an electrode 2210 a′ on the right side and anelectrode 2210 b′ on the left side (from the perspective of theoperator). The right side electrode 2210 a′ defines a first width W₁ anddefines a first gap G₁ between the electrode 2210 a′ and the ultrasonicblade 2208′. The left side electrode 2210 b′ defines a second width W₂and defines a second gap G₂ between the electrode 2210 b′ and theultrasonic blade 2208′. In one aspect the first width W₁ is less thanthe second width W₂ and the first gap G₁ is less than the second gap G₂.A high density polymeric pad 2214′ is located adjacent the softpolymeric pad 2212′ to prevent the ultrasonic blade 2208′ from shortingthe electrodes 2210 a′, 2210 b′. In one aspect, the soft polymeric pads2212′, 2214′ can be made of polymers known under the tradename TEFLON(polytetrafluoroethylene polymers and copolymers), for example.

FIG. 39 is cross-sectional view taken at section 37-37 of the endeffector 2200 shown in FIG. 33, except that the ultrasonic blade 2208′has a different geometric configuration. At the plane where section37-37 the end effector 2200′ is thinner and has more curvature than theend effector 2200′ at section 36-36. The right side electrode 2210 a′defines a third width W₃ and defines a third gap G₃ between theelectrode 2210 a′ and the ultrasonic blade 2208′. The left sideelectrode 2210 b′ defines a fourth width W₄ and defines a fourth gap G₄between the electrode 2210 b′ and the ultrasonic blade 2208′. In oneaspect the third width W₃ is less than the fourth width W₄ and the thirdgap G₃ is less than the fourth gap G₄.

FIG. 40 is a cross-sectional view taken at section 36-36 of the endeffector 2200 shown in FIG. 33, except that the ultrasonic blade 2208″has a different geometric configuration. The end effector 2200″comprises an ultrasonic blade 2208″cacoustically coupled to anultrasonic transducer which is electrically driven by the generator. Theclamp arm 2202″ comprises an electrode 2210 a″ on the right side and anelectrode 2210 b″ on the left side (from the perspective of theoperator). The right side electrode 2210 a″ defines a first width W₁ anddefines a first gap G₁ between the electrode 2210 a″ and the ultrasonicblade 2208″. The left side electrode 2210 b″ defines a second width W₂and defines a second gap G₂ between the electrode 2210 b″ and theultrasonic blade 2208″. In one aspect the first width W₁ is less thanthe second width W₂ and the first gap G₁ is less than the second gap G₂.A high density polymeric pad 2214″ is located adjacent the softpolymeric pad 2212″ to prevent the ultrasonic blade 2208″ from shortingthe electrodes 2210 a″, 2210 b″. In one aspect, the polymeric pads2212″, 2214″ can be made of polymers known under the tradename TEFLON(polytetrafluoroethylene polymers and copolymers), for example.

FIG. 41 is cross-sectional view taken at section 37-37 of the endeffector 2200 shown in FIG. 33, except that the ultrasonic blade 2208″has a different geometric configuration. At the plane where section37-37 the end effector 2200″ is thinner and has more curvature than theend effector 2200″ at section 36-36. The right side electrode 2210 a″defines a third width W₃ and defines a third gap G₃ between theelectrode 2210 a″ and the ultrasonic blade 2208″. The left sideelectrode 2210 b″ defines a fourth width W₄ and defines a fourth gap G₄between the electrode 2210 b″ and the ultrasonic blade 2208″. In oneaspect the third width W₃ is less than the fourth width W₄ and the thirdgap G₃ is less than the fourth gap G₄.

The surgical instruments described herein also can include features toallow the energy being delivered by the generator to be dynamicallychanged based on the type of tissue being treated by an end effector ofa surgical instrument and various characteristics of the tissue. In oneaspect, a technique for controlling the power output from a generator,such as the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), thatis delivered to the end effector of the surgical instrument can includean input that represents the tissue type to allow the energy profilefrom the generator to be dynamically changed during the procedure basedon the type of tissue being effected by the end effector of the surgicalinstrument.

As disclosed herein, techniques for controlling a generator based on thetissue type may be provided. Various techniques can be used to select apower profile to allow the energy being delivered from the generator todynamically change based on the tissue type being treated by thesurgical instrument.

FIG. 42A illustrates an end effector 2300 comprising a clamp arm 2302and an ultrasonic blade 2304, where the clamp arm 2302 includeselectrodes 2306. The end effector 2300 can be employed in one of thesurgical instruments 104, 106, 108 referred to in FIGS. 1-3. In additionto the end effector 122, 124, 125, the surgical instruments 104, 106,108 include a handpiece 105, 107, 109 and a shaft 126, 127, 129,respectively. The end effectors 122, 124, 125 may be used to compress,cut, and/or seal tissue. Referring to FIG. 42A, the end effector 2300,similar to the end effectors 122, 124, 125 shown in FIGS. 1-3, may bepositioned by a physician to surround tissue 2308 prior to compression,cutting, or stapling. As shown in FIG. 42A, no compression may beapplied to the tissue while preparing to use the end effector 2300. Asshown in FIG. 42A, the tissue 2308 is not under compression between theclamp arm 2302 and the ultrasonic blade 2304.

Referring now to FIG. 42B, by engaging the trigger on the handle of asurgical instrument, the physician may use the end effector 2300 tocompress the tissue 2308. In one aspect, the tissue 2308 may becompressed to its maximum threshold, as shown in FIG. 42B. As shown inFIG. 42A, the tissue 2308 is under maximum compression between the clamparm 2302 and the ultrasonic blade 2304.

Referring to FIG. 43A, various forces may be applied to the tissue 2308by the end effector 2300. For example, vertical forces F1 and F2 may beapplied by the clamp arm 2302 and the ultrasonic blade 2304 of the endeffector 2300 as tissue 2308 is compressed between the two. Referringnow to FIG. 43B, various diagonal and/or lateral forces also may beapplied to the tissue 2308 when compressed by the end effector 2300. Forexample, a force F3 may be applied. For the purposes of operating amedical device such as the surgical instruments 104, 106, 108 it may bedesirable to sense or calculate the various forms of compression beingapplied to the tissue by the end effector. For example, knowledge ofvertical or lateral compression may allow the end effector to moreprecisely or accurately apply a staple operation or may inform theoperator of the surgical instrument such that the surgical instrumentcan be used more properly or safely.

In one form, a strain gauge can be used to measure the force applied tothe tissue 2308 by the end effector shown in FIGS. 42A-B and 43A-B. Astrain gauge can be coupled to the end effector 2300 to measure theforce on the tissue 2308 being treated by the end effector 2300. Withreference now also to FIG. 44, in the aspect illustrated in FIG. 44, asystem 2400 for measuring forces applied to the tissue 2308 comprises astrain gauge sensor 2402, such as, for example, a micro-strain gauge, isconfigured to measure one or more parameters of the end effector 2300such as, for example, the amplitude of the strain exerted on a clamp armof an end effector, such as the clamp arm 2302 of FIGS. 43A-B, during aclamping operation, which can be indicative of the tissue compression.The measured strain is converted to a digital signal and provided to aprocessor 2410 of a microcontroller 2408. A load sensor 2404 can measurethe force to operate the ultrasonic blade 2304 to cut the tissue 2308captured between the clamp arm 2302 and the ultrasonic blade 2304 of theend effector 2300. A magnetic field sensor 2406 can be employed tomeasure the thickness of the captured tissue 2308. The measurement ofthe magnetic field sensor 2406 also may be converted to a digital signaland provided to the processor 2410.

Further to the above, a feedback indicator 2414 also can be configuredto communicate with the microcontroller 2408. In one aspect, thefeedback indicator 2414 can be disposed in the handle of a surgicalinstrument, such as those shown in FIGS. 1-3. Alternatively, thefeedback indicator 2414 can be disposed in a shaft assembly of asurgical instrument, for example. In any event, the microcontroller 2408may employ the feedback indicator 2414 to provide feedback to anoperator of the surgical instrument with regard to the adequacy of amanual input such as, for example, a selected position of a firingtrigger that is used to cause the end effector to clamp down on tissue.To do so, the microcontroller 2408 may assess the selected position ofthe clamp arm 2302 and/or firing trigger. The measurements of the tissue2308 compression, the tissue 2308 thickness, and/or the force requiredto close the end effector 2300 on the tissue, as respectively measuredby the sensors 2402, 2404, 2406, can be used by the microcontroller 2408to characterize the selected position of the firing trigger and/or thecorresponding value of the speed of end effector. In one instance, amemory 2412 may store a technique, an equation, and/or a look-up tablewhich can be employed by the microcontroller 2408 in the assessment.

The generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), surgicalinstruments 104, 106, 108 (FIGS. 1-3), and end effectors 122, 124, 125,700, 800, 900, 1000, 1100, 1200, 2200, 2200′, 2200″, 2300 (FIGS. 1-3,14-22, 33-43B) described herein may be employed alone or in combinationto perform surgical procedures in accordance with the techniques andprocesses described hereinbelow. Nevertheless, for conciseness andclarity, the surgical procedures are described with reference to themultifunction surgical instrument 108 and the generator 500. Themultifunction surgical instrument 108 comprises an end effector 125which includes a clamp arm 145 and an ultrasonic blade 149. The endeffector 125 may be configured with any of the structural or functionalfeatures of any one of the end effectors 122, 124, 125, 700, 800, 900,1000, 1100, 1200, 2200, 2200′, 2200″, 2300 to provide electrodes toapply RF energy to tissue, temperature sensors, force/pressure sensors,and gap measurement sensors, as described hereinabove.

Techniques for Determining Tissue Coefficient of Friction/TissueCoefficient of Coagulation

In one aspect, the present disclosure provides a technique fordetermining a tissue coefficient of friction/tissue coefficient ofcoagulation to control the power output from a generator, such as anyone of the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), or asurgical instrument, such as the surgical instrument 108 (FIGS. 1-3).The power delivered to an end effector of a surgical instrument can varybased on a tissue coefficient of friction. The energy profile from thegenerator can be adjusted based on the tissue coefficient of frictionand dynamically switched during the procedure between RF and ultrasonicenergy modalities based on the tissue impedance to treat the tissueclamped between a clamp arm and an ultrasonic blade of the end effectorof the surgical instrument. For conciseness and clarity of disclosure,the techniques for determining a tissue coefficient of friction will bedescribed with reference to the multifunction surgical instrument 108 ofFIG. 2 coupled to the generator 500 of FIG. 8, although it will beappreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

The following description provides techniques for determining a tissuecoefficient of friction μ. In order to accurately calculate the tissuecoefficient of friction μ of the tissue 2308, the force applied to thetissue 2308 must be in a certain range to ensure that there issufficient contact between the tissue 2308 and the end effector 2300 andthat therapeutic amounts of energy are being delivered to the endeffector 2300. For example, in one aspect, a minimum load on the tissue2308 can be 1.5 lbs. to ensure that there is enough contact between thetissue 2308 and the end effector 2300, and a maximum load on the tissue2308 can be 2.2 lbs. to ensure that a therapeutic amount of energy isbeing used. These values can be used with a power level 1. In addition,the force is measured using any of the above measurement components andtechniques at various loads on the tissue 2308. At least twomeasurements can be taken at two different loads. For example, power canbe measured at 1.76 lbs. (800 grams) and 2.2 lbs. (1000 grams) in orderto graph power versus force. It can be more accurate, however, to takemeasurements at a plurality of loads and store the values in a buffer.In one form, a buffer can be filled with values for each incrementalgram between 2400 grams and 1000 grams and can use various rules, suchas the first in first out rule, to store the values until the slopevalue is maximized. A new regression can be performed each time a newvalue is added to the buffer and a value is dropped from the buffer.Various other methods can be used as well to calculate the slope value.

A functional model for heating of tissue can be represented in a simplefrictional model:{dot over (Q)}=μ·v·N  Equation 1where {dot over (Q)} is the rate of heat generation, v is the rmsvelocity of the ultrasonic motion at the tip of the blade, and N is thenormal force driving tissue against the ultrasonic blade. The tissuecoefficient of friction, μ, is the proportionality constant that makesthe statement true and it relates to tissue properties. It is thereforereferred to as the tissue coefficient of friction μ and may be referredto interchangeably as the tissue coefficient of coagulation. As is knownin the art, friction is the force resisting the relative motion of solidsurfaces, fluid layers, and material elements sliding against eachother.

In practice, {dot over (Q)} is the measured amount power equal to theproduct of the rms values of current and voltage when driven at zerophase. The velocity is the product of the rms displacement, d, times theradian frequency or v=2πf·d. In the case of an ultrasonic surgicalsystem this is the frequency at resonance which equals 55.5 kHz for theultrasonic system. Furthermore d is proportional to the current drivingthe system, which is set by the level on the generator. The factor v isreadily calculated. N is the normal force which is either set by theinstrument design at full trigger closure or can be measured with aforce gage/strain gage. Since {dot over (Q)}, v, and N are calculablefrom known parameters, then can be estimated by rearranging Equation 1:

$\mu = \frac{\overset{.}{Q}}{v \cdot N}$

Note that removing the quiescent power from {dot over (Q)} and updatingthe frequency f as the resonance drifts lower, will increase therepeatability and accuracy of the estimated tissue coefficient offriction μ. In order to determine the type of tissue being treated bythe end effector of the surgical instrument, a tissue coefficient offriction μ can be calculated. The calculated tissue coefficient offriction is compared to a database of tissue coefficients of frictionthat correlates each tissue coefficient of friction with a tissue type,as will be discussed in more detail below. The calculated tissuecoefficient of friction and its related tissue type are used by atechnique to control the energy being delivered from the generator tothe surgical instrument. In one form, the tissue coefficient of frictionμ is described by the above where {dot over (Q)} is the rate of heatgeneration, v is the velocity of the ultrasonic motion of the endeffector, and N is the force applied to the tissue by the end effector.The velocity v of the ultrasonic motion is a known value from thesettings of the generator. Since the value v is a known value, thetissue coefficient of friction μ can be calculated using the slope of agraph of heat generation versus force on the tissue.

The force applied to the tissue by the end effector can be measured in avariety of ways using different type of components to measure force.This force measurement can be used, for example in the equation above,to determine the tissue coefficient of friction of the tissue beingtreated to determine its tissue type.

Looking at the equation {dot over (Q)}=μ·v·N the product of the tissuecoefficient of friction and velocity, μ·v, is the slope of the relationof heat generation and normal load. Because v is known, μ can bedetermined by the slope of a graph of heat generation versus normalload. An example of a graph 2500 of power (Watts) shown along thevertical axis versus force (g) shown along the horizontal axis asmeasured with a plurality of plotted data points is illustrated in FIGS.45-46. FIG. 45 illustrates graphs 2500 for a porcine carotid curves2502, 2504 at two different power levels, porcine bowel curve 2506, anddry chamois curve 2508. The data for a carotid artery at Level 3 is alsoshown. These are single measurements and there are no means and standarddeviations to test for differences. While ideally the values of thetissue coefficient of friction μ at Levels 1 and 3 should be the same,the values at 0.30 and 0.35 are sufficiently close to believe that μ isan intrinsic property of the tissue.

FIG. 46 illustrates the same graphs 2500′ as FIG. 45, but only thesections of each graph that are substantially linear. The linearsections 2502′, 2504′, 2506′, 2508′ of each curve 2502, 2504, 2506, 2508(FIG. 45) are located in the region of the curve where the force wasgreater than the initial low level of force used. Each of the linearsections 2502′, 2504′, 2506′, 2508′ can be modeled as a regression linein the form of:y=mx+b  Equation 2where y is the dependent variable (Power [Watts]), x is the independentvariable (Force [g]), m is the slope of the line, and b is they-intercept.

Each of the linear sections 2502′, 2504′, 2506′, 2508′ also arecharacterized by R-squared (R²), where R² is a statistical measure ofhow close the data are to the fitted regression line y. It is also knownas the coefficient of determination, or the coefficient of multipledetermination for multiple regression. The definition of R² is thepercentage of the response variable variation that is explained by thelinear model y. In other words:R ²=Explained variation/Total variation

R² is always between 0 and 100% where 0% indicates that the modelexplains none of the variability of the response data around its meanand 100% indicates that the model explains all the variability of theresponse data around its mean. In general, the higher the R², the betterthe model fits the data.

In the example illustrated in FIG. 46, the regression line and R² forthe linear section 2502′ representing porcine carotid tissue at powerlevel 1 are:y=0.0137x+0.2768R ²=0.9902

The regression line and R² for the linear section 2504′ representingporcine carotid tissue at power level 3 are:y=0.0237x+8.9847R ²=0.978

The regression line and R² for the linear section 906′ representingbowel tissue at power level 1 are:y=0.0085x+10.587R ²=0.9147

The regression line and R² for the linear section 2508′ representingchamois tissue at power level 1 are:y=0.034x+0.0735R ²=0.9949

The calculated tissue coefficient of friction μ is compared to adatabase of tissue coefficients of friction that correlated eachcoefficient with a tissue type. For example, Table 1 includes exampletissue coefficients of friction μ as calculated from the plots of powerand force illustrated in FIGS. 45-46 for each of the porcine carotidcurves 2502, 2504 at two different power levels, porcine bowel curve2506, and dry chamois curve 2508.

TABLE 1 Coefficient of Tissue Type Power Level Friction μ Porcinecarotid 1 0.30 Porcine carotid 3 0.35 Porcine bowel 1 0.19 Dry chamois 10.75Assumptions: Ultrasonic bade amplitude is nominally 75 μm p-p at level 5and the frequency f is 55.5 kHz. It will be appreciated that the powerlevels referenced above are specific to the LCS product and level 5 ofthe GEN11 generator available from Ethicon Endo-Surgery, Inc. that iscompatible with devices known under the tradename HARMONIC and ENSEAL,also available from Ethicon Endo-Surgery, Inc.

It should be noted that the tissue coefficient of friction μ for theporcine carotid tissue at various power levels should be the same as thetissue coefficient of friction μ is a value intrinsic to the tissue. Thevalues of 0.30 and 0.35 for the calculated tissue coefficients offriction μ are substantially close enough to show that the tissuecoefficient of friction μ is intrinsic to the tissue itself.

One technique for determining the slope is to measure power delivered attwo loads. Assuming Level 1 is used for this calculation, then the powercould be measured at nominally 800 grams (1.76 lbs) and 1000 grams (2.2lbs). However just using the two points can be inaccurate. It is betterto fill a buffer of approximately 201 points for every gram in the 800to 1000 gram range inclusive. The buffer could be slide advanced using afirst-in-first-out (FIFO) rule until the R² value is maximized. A newregression would be performed each time a new point is added and an oldpoint is dropped. Other schemes can be envisioned as well. Thecalculated slope is then compared with known values for specific tissuetypes. For example if the calculated slope is in the region of 0.30 to0.35, then an artery is determined to be in the jaws. If the values arein the range of 0.15 to 0.20 then a section of bowel is determined to bein the jaws. In one technique, the R² value may be used as an indicationof specificity. For example if R² is less than 0.90, for example, thenan indication is given that a determination cannot be made. R² values inthe range of 0.60 to 1.00 may be used to indicate that a determinationof tissue type can be made and preferably tis threshold may be about0.90.

In practice, sampling would be done on a time basis and both power andforce would be sampled. These configurations are captured in the logicflow diagram of FIG. 47. The technique can be implemented in thegenerator software and/or the surgical instrument software.

It will be appreciated that using the averages for power and force attwo positions can improve the accuracy of a two-point slope calculation.For accuracy it may be necessary to measure closure force (and moment)in addition to power.

The benefits of using the tissue coefficient of friction μ as a means tocharacterize tissue is discussed hereinbelow in connection with FIG. 48.Accordingly, the tissue coefficient of friction μ can be used todiscriminate tissues and can be calculated using a technique forincluding steps to determine that a selection cannot be made.

FIG. 47 illustrates a logic flow diagram 2600 of one form of a methodfor dynamically changing the energy delivered to a surgical instrumentbased on a determination of tissue type being treated by the instrument.As described herein, the logic flow diagram 2600 may be implemented inthe generator 500, the multifunction surgical instrument 108, or acombination thereof. With reference now to the logic flow diagram 2600shown in FIG. 47, a characterization mode of the system is started bythe processor 502 in which the type of tissue being treated by thesurgical instrument is determined 2602 by the processor 502. The endeffector 125 is positioned such that tissue is positioned within theclamp arm 145 and the ultrasonic blade 149 of the end effector 125. Theclamp arm 145 is used to apply a force to the tissue. The force of theend effector 125 on the tissue is measured and compared 2604 by theprocessor 502 to a threshold minimum force. If the force applied to thetissue is below a minimum threshold force, the force applied to thetissue is increased 2606 and is again measured and compared 2604 by theprocessor 502 to the threshold minimum force.

Once the force on the tissue has reached the minimum threshold force,the processor 502 samples 2608 the force applied to the tissue and thepower delivered to the end effector 125 by the generator 500 and saves2612 the samples in a buffer. The processor 502 determines 2610 whetherthe buffer is full. Samples are saved 2612 in the buffer until thebuffer is full, and then the processor 502 utilizes the samples to plot2614 points on a graph of force versus power. This information is usedby the processor 502 to calculate and store 2616 the slope and R² valuesin a database. See FIG. 46, for example, for a graphical representationof the linear sections of power versus force plots including thecoefficient of determination R². Once stored in the database, theprocessor 502 compares the force values to a maximum force threshold anddetermines 2618 when the force reaches a maximum threshold value. Untilthe force reaches the maximum threshold value, the processor 502continues along the NO branch and continues sampling 2608 the nextsamples of power and force. The processor 502 repeats until the forcereaches the maximum threshold.

Once the force has reached the maximum threshold, the samples are nolonger taken and stored and the processor 502 continues along the YESbranch to select 2620 the slope with the highest R² value and tocalculate the tissue coefficient of friction μ. Next, the processor 502determines 2622 if the maximum slope value R² is greater than apredetermined threshold. If R² is less than the predetermined threshold,then the confidence level is low and the slope value cannot be used tocalculate the tissue coefficient of friction μ and identify the tissuetype and the processor 502 continues along the YES branch to display2624 a message indicating that the tissue type has not been identified.In one aspect, the threshold may be selected in the range of 0.6 to 1.00and may preferably be set to about 0.90, for example. In other aspects,the threshold may be selected using more sophisticated, statisticaltests applied to determine the level confidence R². If R² is greaterthan or equal to the predetermined threshold, the calculated tissuecoefficient of friction μ can be used to identify the tissue and theprocessor 502 continues along the NO branch where the processor 502compares 2626 the calculated tissue coefficient of friction μ to adatabase 2628 of stored tissue coefficients of friction μ which thestored tissue coefficients of friction μ correspond to tissue types. Thetissue type is selected 2630 and displayed and used to specify 2632 thepower delivery profile for delivering energy from the generator 500 tothe end effector 125 of the surgical instrument 108. Normal operationmode is entered 2634 such that the tissue type and related powerdelivery profile are used to control the end effector 125 for treatingthe tissue.

In one aspect, the tissue coefficient of friction μ and its rate may beemployed to determine tissue type and power delivery profile. Forexample, It has been shown in preliminary work that μ is significantlydifferent between porcine bowel, artery and chamois. Furthermore the μvalues were initial flat but did change as time progressed presumablybecause of the temperature rise as heat was added. From theseobservations, μ can be used as a tissue differentiator and can be doneat lower current to avoid rapid changes in μ when the purpose is tocharacterize the tissue. Also, another parameter of interest would bethe rate of change of the tissue coefficient of friction μ for fixedconditions of {dot over (Q)}, v, and N. It will be appreciated that μ isnot simply differentiating the equation

$\mu = \frac{\overset{.}{Q}}{v \cdot N}$with respect time, because the change is due to changes in the tissueitself. For example the μ for chamois rapidly rises when heat isdelivered compare with carotid arteries or bowel, because it is dry. Therate of change is likely dependent on the percentage of water content inthe tissue. In one aspect, the present disclosure provides a techniqueto estimate both the tissue coefficient of friction μ and the rate ofchange of the tissue coefficient of friction μ and compare them withtable of know values stored in a database, for example. The tissueselection can be based on the values closet to the estimated values. Thepower delivery profile could then be optimize for that tissue anddelivered to the surgical instrument 108. Estimating the tissuecoefficient of friction μ and the rate of change of the tissuecoefficient of friction μ may be able to further differentiate tissuetypes. Another aspect of the present disclosure includes tracking thetissue coefficient of friction μ as the seal/transection progresses. Keychanges in this parameter may signal a need to modify the power deliveryprofile.

FIG. 48 illustrates a logic flow diagram 2700 of another form of amethod for dynamically changing the energy delivered to a surgicalinstrument 108 based on a determination of tissue type being treated bythe surgical instrument 108. As described herein, the logic flow diagram2700 may be implemented in the generator 500, the multifunction surgicalinstrument 108, or a combination thereof. With reference now to thelogic flow diagram 2700 shown in FIG. 48 and the surgical system 100 ofFIG. 1, the processor 502 initiates a power evaluation mode of thesystem to determine 2702 the power profile for the generator 500. Theend effector 125 of the surgical instrument 108 is then engaged with thetissue to be treated and the end effector 125 of the surgical instrument108 is activated 2704 with energy delivered from the generator 500. Thetissue coefficient of friction μ and the processor 502 measures 2706 therate of change (e.g., rate of rise) of the tissue coefficient offriction μ over a short period of time. The processor 502 compares 2708the measured tissue coefficient of friction μ and the rate of change ofthe tissue coefficient of friction μ to values stored in a tissueinformation database 2714.

If the system is in learning mode, in which the tissue informationdatabase 2714 information regarding tissue type and tissue coefficientsof friction μ are being updated, the tissue type can be visuallyidentified 2710. The processor 502 updates 2712 the tissue informationdatabase 2714 of tissue coefficient of friction μ and tissue typeinformation to increase the accuracy of the tissue information database2714.

If the system is not in learning mode, then the processor 502 selects2716 a power delivery profile based on the determined tissue andsurgical instrument type 2718 being used. During the treatment of thetissue, the processor 502 continues to calculate and monitor 2720 thetissue coefficient of friction μ and the rate of change of the tissuecoefficient of friction μ to allow the processor 502 to dynamicallyupdate the power delivery profile. If an error is found, the powerdelivery profile is modified 2724. The processor 502 then determines2722 if the correct pattern of power and delivery profile is being used.If no error is found, the current power delivery profile continues 2726.Otherwise, the processor 502 modifies 2724 the power and deliveryprofile. The processor 502 continues the process of verification andcorrection of the power delivery profile during the entire surgicalprocedure to optimize the energy being delivered to the surgicalinstrument 108 based on the type of tissue being treated.

Techniques for Controlling a Generator Based on the Hydration Level ofTissue

In one aspect, the present disclosure provides a technique forcontrolling the power output from a generator, such as any one of thegenerators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), or a surgicalinstrument, such as the surgical instrument 108 (FIGS. 1-3). The powerdelivered to the end effector of the surgical instrument can becontrolled based on the hydration level of the tissue to allow theenergy profile from the generator to be dynamically changed based on thehydration level of the tissue being treated by the end effector of thesurgical instrument. For conciseness and clarity of disclosure, thetechniques for controlling the power output from a generator based onthe hydration level of tissue will be described with reference to themultifunction surgical instrument 108 of FIG. 2 coupled to the generator500 of FIG. 8, although it will be appreciated that other configurationsof instruments, generators, and end effectors described herein may bereadily substituted without departing from the scope of the presentdisclosure.

In order to determine the hydration level of the tissue being treated bythe end effector 125 of the surgical instrument 108, the tissuecoefficient of friction μ as described herein can be used. As explainedabove, a force measurement is taken using any of the methods describedherein to calculate the tissue coefficient of friction μ to determinethe hydration level of the tissue. The calculated tissue coefficient offriction μ is compared to a database of tissue coefficients of frictionμ that correlate each tissue coefficient with a hydration level of thetissue. The calculated tissue coefficient of friction μ and its relatedtissue hydration level are used by the technique to control the energybeing delivered from the generator 500 to the surgical instrument 108.

The hydration level of the tissue can be indicative of a variety ofconditions within the tissue. During a coagulation cycle in which RFenergy is being used to coagulate the tissue, a decrease in the tissuehydration level can indicate that the tissue is nearing the end of thecoagulation cycle. In addition, the hydration level of the tissue canvary during the coagulation cycle such that the RF energy beingdelivered from the generator 500 can dynamically change during thecoagulation cycle based on the calculated hydration levels during thecycle. For example, as a coagulation cycle progresses, the hydrationlevel of the tissue will decrease such that the technique used tocontrol the energy delivered from the generator 500 can decrease thepower as the cycle progresses. Thus, the hydration level of the tissuecan be an indicator of the progress through a coagulation cycle of thetissue by the end effector of the surgical instrument 108.

FIG. 49 illustrates a logic flow diagram 5900 of one form of a methodfor dynamically changing the energy delivered to a surgical instrument108 based on a determination of the hydration level of tissue beingtreated by the surgical instrument 108. As described herein, the logicflow diagram 5900 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 5900 shown in FIG. 49, theprocessor 502 determines the hydration level of the tissue by measuringthe tissue coefficient of friction μ as described herein. Initially, theend effector 125 of the surgical instrument 108 is closed on tissue andthe end effector 125 is activated 5902 with energy from the generator500. The processor 502 measures 5904 the tissue coefficient of frictionμ, as described herein. The processor 502 compares 5906 the tissuecoefficient of friction μ and the rate of change of the tissuecoefficient of friction to values stored in a database to determine thehydration level of the tissue. The processor 502 selects 5908 a powerdelivery profile based on the hydration level of the tissue. Theprocessor 502 monitors 5910 the tissue coefficient of friction μ and therate of change of the tissue coefficient of friction μ during treatmentof the tissue to monitor the changes in the tissue hydration level. Thisallows the processor 502 to dynamically change 5912 the power deliveryprofile, such that power delivered from the generator 500 candynamically change during tissue treatment.

Techniques for Switching Between RF and Ultrasonic Energy Based onTissue Type

In another aspect, the present disclosure provides a technique forcontrolling energy delivered by a generator and/or a surgical instrumentby dynamically switching between RF and ultrasonic energy. The techniqueincludes controlling the power output from a generator, such as any oneof the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), or asurgical instrument, such as the surgical instrument 108 (FIGS. 1-3). Inone aspect, RF and ultrasonic energy can be dynamically switched basedon the type of tissue being treated by an end effector of a surgicalinstrument and various characteristics of the tissue. The powerdelivered to the end effector of the surgical instrument can include aninput that represents the tissue type to allow the energy profile fromthe generator to be dynamically changed between RF and ultrasonic energyduring the procedure based on the type of tissue being effected by theend effector of the surgical instrument. For conciseness and clarity ofdisclosure, techniques for dynamically switching between differentenergy modalities, such as, for example RF energy and ultrasonic energy,will be described with reference to the multifunction surgicalinstrument 108 of FIG. 2 coupled to the generator 500 of FIG. 8,although it will be appreciated that other configurations ofinstruments, generators, and end effectors described herein may bereadily substituted without departing from the scope of the presentdisclosure.

In order to determine the type of tissue being treated by the endeffector 125 of the surgical instrument 108, a tissue coefficient offriction μ and/or the rate of change of the tissue coefficient offriction μ can be calculated and compared to a database of tissuecoefficient of friction μ that correlates each tissue coefficient offriction μ with a tissue type, as explained above. The calculated tissuecoefficient of friction μ and its related tissue type are used by atechnique to control the type (RF or ultrasonic) and power level ofenergy being delivered from the generator 500 to the surgical instrument108. Tissue types include, without limitation, tissue with a muscularstructure, tissue with a vascular structure, tissue with a thinmesentery structure.

FIG. 50 illustrates a logic flow diagram 2900 of one aspect of a methodof dynamically changing the between RF energy delivered from theENERGY2/RETURN output of the generator 500 and ultrasonic energydelivered from the ENERGY1/RETURN output of the generator 500 to thesurgical instrument 108 based on a determination of tissue type beingtreated by the surgical instrument 108. As described herein, the logicflow diagram 2900 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 2900 shown in FIG. 50, theprocessor 502 initiates a characterization mode of the generator 500 todetermine 2902 the type of tissue being treated by the surgicalinstrument 108. The end effector 125 is positioned such that tissue ispositioned between the clamp arm 145 and the ultrasonic blade 149 of theend effector 125. The end effector 1255 applies a force to the tissue.The force applied to the tissue by the end effector 125 is measured andcompared 2904 by the processor 502 to a threshold minimum force. If theprocessor 502 determines that the force applied to the tissue is below aminimum threshold force, the force applied to the tissue is increased2906. Once the force on the tissue has reached the minimum thresholdforce, the processor 502 samples 2908 the force applied to the tissueand the power delivered to the end effector 125 by the generator 500 andstores the samples in a buffer.

The processor 502 determines 2901 if the buffer is full. If the bufferis not full, the processor 502 enters 2912 the most recent samples intothe buffer. If the buffer is full, the processor 502 enters the mostrecent samples into the buffer and drops 2914 the first point (e.g.,FIFO method for organizing and manipulating a data buffer). Theprocessor 502 calculates and stores 2916 the slope and R² values and theforce is tested to determine 2918 if the force applied to the tissue isgreater than a maximum force threshold. If the force applied to thetissue is not greater than the maximum threshold, the processor 502samples 2908 the force applied to the tissue and the power delivered tothe end effector 125 by the generator 500 and saves the samples in abuffer. The processor 502 repeats until the force applied to the tissueis greater than the maximum threshold. The processor 502 selects theslope with the highest R² and calculates 2920 the tissue coefficient offriction μ. If the processor 502 determines 2922 that R² is less than apredetermined threshold, the processor 502 continues along the YESbranch and the system displays 2924 that the tissue type was notidentified. If R² is greaten than or equal to the threshold, theprocessor 502 continues along the NO branch and compares 2926 thecalculated tissue coefficient of friction μ to values stored in a tissueinformation database 2928.

In one aspect, the threshold may be selected in the range of 0.6 to 1.00and may preferably be set to about 0.90, for example. In other aspects,the threshold may be selected using more sophisticated, statisticaltests applied to determine the level confidence R². In one aspect, thethreshold may be selected between 0.6 to 1.00 and may preferably be setto about 0.90. In other aspects, the threshold may be selected usingmore sophisticated, statistical tests applied to determine the levelconfidence R². The processor 502 then selects 2930 and displays thetissue type and specifies 2932 the power delivery profile for deliveringeither ultrasonic energy (ENERGY1/RETURN) or RF energy (ENERGY2/RETURN)from the generator 500 to the end effector 125 of the surgicalinstrument 108. Normal operation mode is entered 2934 such that thetissue type and related power delivery profile are used to control theend effector for treating the tissue. Using the tissue type determinedin accordance with the logic flow diagram 2900, the processor 502 canprovide optimized energy delivery for that particular tissue. Tissuetypes that are determined to be more vascular or muscular would requiremore RF energy at the beginning of the cycle to provide more sealingenergy either before the application of the ultrasonic energy or at ahigher ratio of RF vs. ultrasonic energy. And tissue types that are lessvascular would require less RF energy at the beginning of the cycle andthe system would change the energy delivery toward a cutting profileusing ultrasonic energy. Energy may be applied to the tissue until thetissue meets or exceeds a predetermined threshold impedance, which maybe referred to as the termination impedance, and which is the tissueimpedance that corresponds to the impedance of tissue when the tissueseal is complete.

Techniques for Dynamically Changing the Energy Delivered from aGenerator Based on Aperture Defined by the End Effector and EnergyParameters

In one aspect, the present disclosure provides a technique fordynamically changing the energy delivered from a generator based on anaperture defined by an end effector. According to one aspect, thetechniques for dynamically changing the energy delivered from agenerator, such as any one of the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), or a surgical instrument, such as the surgicalinstrument 108 (FIGS. 1-3). For conciseness and clarity of disclosure,techniques for dynamically changing energy delivered from a generatorbased on an aperture defined by an end effector and energy parameterswill be described with reference to the multifunction surgicalinstrument 108 of FIG. 2 coupled to the generator 500 of FIG. 8,although it will be appreciated that other configurations ofinstruments, generators, and end effectors described herein may bereadily substituted without departing from the scope of the presentdisclosure.

The energy profile from the generator 500 can be dynamically changedduring the procedure between RF and ultrasonic energy based on theaperture defined by the end effector 125 that is clamping on a tissue.This allows the generator 500 to switch from RF energy to ultrasonicenergy based on the amount of clamping force exerted by the end effector125 on the tissue being treated by the surgical instrument 108. Theaperture defined by the clamp arm 145 is related to the creation of aproper coagulation seal, for example, when RF energy is being deliveredfrom the generator 500 to the end effector 125 of the surgicalinstrument 108, such that RF energy should be used when there is asufficient closure of the end effector 108 on the tissue. Thus, when theaperture defined by the end effector 108 is too large and there is not asufficient clamping force exerted on the tissue for proper coagulation,only ultrasonic energy is delivered to the ultrasonic blade 149 of theend effector 125 through the ENERGY1/RETURN output of the generator 500.

For example, misleading information regarding various tissuemeasurements and/or characteristics can be transmitted to the generator500 for use in the techniques for controlling the energy delivereddepending on the aperture defined by the end effector 125. One suchmeasurement that can be affected by the aperture defined by the endeffector 125 is tissue impedance. Tissue impedance measured by aninstrument as described herein will depend on several factors includingthe clamping force or pressure applied by the end effector 125 and thedistance between electrodes in the case of RF energy or the clamp arm145 aperture in the case of ultrasonic energy. Many techniques thatdetermine the end of the coagulation cycle depend on the tissueimpedance. A clamp arm 145 that is not fully closed on the ultrasonicblade 149 can lead to a tissue impedance determination that may notproperly represent the condition of the tissue. An incorrect tissueimpedance determination can lead to early termination of a coagulationcycle as the generator 500 may switch from RF to ultrasonic energybefore a proper coagulation seal has been achieved. In one aspect, thetissue impedance may be determined by the processor 502 by dividing theoutput of the second voltage sensing circuit 524 coupled across theterminals labeled ENERGY2/RETURN by the output of the current sensingcircuit 514 is disposed in series with the RETURN leg of the secondaryside of the power transformer 508 as shown in FIG. 8. The outputs of thevoltage sensing circuit 512 are provided to an isolation transformer andADC 516 and the output of the current sensing circuit 514 is provided toanother isolation transformer and ADC 518 to provide the voltage andcurrent measurement is digital form to the processor 502.

The aperture defined by the end effector 125 can be determined using avariety of techniques. In various aspects, the aperture defined by theend effector 125 may be determined by detecting the pivot angle of theend effector 125. This can be accomplished using a potentiometer, a Halleffect sensor (in a manner described in connection with FIG. 19), anoptical encoder, an optical IR sensor, an inductance sensor, orcombinations thereof. In another aspect, the proximity of first andsecond components of an end effector is measured to determine theaperture defined by the end effector using, for example, the Hall effectsensor, an optical encoder, an optical IR sensor, an inductance sensor,or combinations thereof. In another aspect, the surgical instrument 108may be configured to detect the aperture defined by the end effector 125by measuring a change in a tissue impedance of the tissue interactingwith the end effector. In another aspect, the surgical instrument 108may be configured to detect the aperture defined by the end effector 125by measuring a load applied by the end effector 125 on the tissue asultrasonic energy is pulsed to the end effector 125. In another aspect,the surgical instrument 108 includes a switch or other mechanism forclosing the end effector 125 that can detect the aperture defined by theend effector 125. In another aspect, the aperture defined by the endeffector 125 may be determined based on linear displacement or stroke ofthe closure mechanism located either in the shaft 129 or the handle 109of the surgical instrument 108. In another form, the aperture defined bythe end effector 125 may be determined by the angular displacement ofthe trigger mechanism located in the handle 109 of the surgicalinstrument 108.

FIG. 51 is a logic flow diagram 3000 of one aspect of a technique fordynamically changing the energy delivered from a generator based onaperture defined by the end effector and energy parameters. As describedherein, the logic flow diagram 3000 may be implemented in the generator500, the surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 3000 shown in FIG. 51 and thesurgical system 100 of FIG. 1 with the combination electrosurgical andultrasonic multifunction surgical instrument 108 and the generators 102,200, 300, 400, 500 (FIGS. 1-3 and 4-8), the aperture defined by the endeffector 125 is determined as described herein. Initially, the endeffector 125 of the surgical instrument 108 is closed on tissue, asshown in FIGS. 42A-B, 43A-B, and the end effector 125 is activated 3002with energy from the generator 500, for example. The aperture defined bythe end effector 125 is determined 3004 by the processor 502 using anyof the techniques described herein. Once the aperture defined by the endeffector 125 is determined 3004, the processor 502 signals the waveformgenerator 504 to delivery energy from the generator 500 and controlsswitching the output of the generator 500 between RF energy ENERGY2 andultrasonic energy (ENERGY1/RETURN) based on the determined aperturedefined by the end effector 125. Accordingly, the processor 502 selects3006 a power delivery profile based on the aperture defined by the endeffector 125. The processor 502 continues to monitor 3008 the aperturedefined by the end effector 125 during the tissue treatment process anddynamically changes 3010 the energy delivered from the generator 500based on the changing aperture defined by the end effector 125.

In another aspect, a technique for controlling the power output from thegenerator, such as the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and4-8), or the surgical instrument 108, such as the surgical instrument108 (FIGS. 1-3) that is delivered to the end effector 125 of thesurgical instrument 108 can include an input that includes energyparameters based on an aperture defined by the end effector 125 of thesurgical instrument 108. The energy profile from the generator 500 canbe dynamically changed during the procedure between RF and ultrasonicenergy using the energy parameters based on the aperture defined by theend effector 125 that is clamping on tissue as shown in FIGS. 42A-B,43A-B. This allows the generator 500 to switch from RF energy ENERGY2 toultrasonic energy (ENERGY1/RETURN) based on the clamping force appliedby the end effector 125 to the tissue being treated by the surgicalinstrument 108. As explained above, the aperture defined by the clamparm 145 is related to creating a proper coagulation seal, for example,when RF energy is being delivered from the generator 500 to the endeffector 125 of the surgical instrument 108, such that RF energy shouldbe used when there is a sufficient closure of the end effector 125 onthe tissue. Thus, when the aperture defined by the end effector 125 istoo large and the clamping force applied to the tissue is insufficientfor proper coagulation, only ultrasonic energy is delivered to the endeffector 125 by the generator 500.

The aperture defined by the end effector 125 can be determined using anyof the methods described herein. For example, the surgical instrument108 can include an aperture defined by a sensor located in the endeffector 125 that can be fed through a connector to the ASIC in thehandle 109 of the surgical instrument 108. The surgical instrument 108also can include a sensor in the handle 109 of the surgical instrument108 that is configured to detect the aperture defined by the endeffector 125.

Energy parameters are configured to be loaded into the generator 500,and can include a plurality of different parameters, including but notlimited to voltage, current, power, and one or more techniques for usein treating tissue. These parameters can be related to the RF energy andultrasonic energy that can be delivered from the generator 500. Theenergy parameters can include information such as maximum and/or minimumvalues to be used to control the energy delivered from the generator500. The energy parameters can be stored in a variety of locations,including an EEPROM on the surgical instrument or some othernon-volatile memory. In addition, there can be multiple sets of energyparameters. For example, there can be a first set of energy parametersthat are used to optimize tissue transection, and a second set of energyparameters that are used to optimize tissue spot coagulation. It will beunderstood that there can be any number of set of energy parameters thatcorrespond to various types of tissue treatments to allow the generatorto switch between the various sets of energy parameters based on thenecessary tissue treatments.

When the end effector 125 of the surgical instrument 108 is activated,one or more of the various techniques described herein are used todetect the aperture defined by the end effector 108. In one aspect, whenthe end effector 125 is closed around the tissue, the generator 500 canutilize the energy parameters for optimizing tissue transection. Whenthe end effector 125 has a larger aperture and is not clamped on thetissue, the generator 500 can utilize the energy parameters foroptimizing spot coagulation of the tissue.

FIG. 52 is a logic flow diagram 3200 of one aspect of a technique fordynamically changing the energy delivered from a generator based onaperture defined by the end effector and energy parameters. As describedherein, the logic flow diagram 3200 may be implemented in the generator500, the multifunction surgical instrument 108, or a combinationthereof. With reference now to the logic flow diagram 3100 shown in FIG.52, with the combination electrosurgical and ultrasonic instrument 108and the generator 500, initially the aperture defined by the endeffector 125 is determined by the processor 502 as described herein. Theend effector 125 of the surgical instrument 108 is closed on tissue, asshown in FIGS. 42A-B, 43A-B, and the end effector 125 is activated withenergy from the generator 500. The aperture defined by the end effector125 is determined 3104 using any of the techniques described herein. Theprocessor 502 signals the waveform generator 504 to deliver energy fromthe generator 500 to the end effector 125 and switch the generator 500output between to switch between RF and ultrasonic energy based on theaperture defined by the end effector 125 by using one of the sets ofenergy parameters that was previously loaded into the generator 500.Accordingly, energy parameters are communicated 3106 to the generator500 based on the previously determined 3104 aperture defined by the endeffector 125. The processor 502 monitors 3108 the aperture defined bythe end effector 125 during the tissue treatment process such that theenergy delivered from the generator 500 can be dynamically communicated3110 by the processor 502 during the tissue treatment process based onthe changing aperture defined by the end effector 125. This allows thegenerator 500 to dynamically switch between the various sets of energyparameters based on the changing aperture defined by the end effector125.

It will be understood that various combinations of information can beused to determine which set of energy parameters are to be used duringtissue treatment. For example, the aperture defined by the end effectorand calculated tissue impedance can be used to determine which set ofenergy parameters are needed to control the energy being delivered fromthe generator.

Techniques for Dynamic Sensing of Tissue

In one aspect, the present disclosure provides dynamic tissue sensingtechniques. In one aspect, the dynamic tissue sensing techniques may beimplemented with a generator, such as any one of the generators 102,200, 300, 400, 500 (FIGS. 1-3 and 4-8), or a surgical instrument, suchas the surgical instrument 108 (FIGS. 1-3). For conciseness and clarityof disclosure, the dynamic tissue sensing techniques will be describedwith reference to the multifunction surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

Upon measuring the tissue thickness and the normal force on theultrasonic blade as shown in and described in connection with FIGS.42A-B, 43A-B, and measuring the tissue coefficient of friction μ, in oneaspect a technique is provided that pulses to measure the tissuecoefficient of friction μ at set time intervals and based on themeasured coefficient μ over time, adjusts the power delivered by any oneof and the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), orthe surgical instrument (FIGS. 1-3), in order to transect or “cut”tissue efficiently and with good hemostasis. In one aspect, a sensingtechnique is configured to monitor tissue friction and determine thetissue coefficient of friction μ, as described herein, throughout a cutand modulates energy delivered during the cut based on change in thetissue coefficient of friction μ over time.

FIG. 53 is a logic flow diagram 3200 of one aspect of a dynamic tissuesensing technique. As described herein, the logic flow diagram 3200 maybe implemented in the generator 500, the multifunction surgicalinstrument 108, or a combination thereof. With reference now to thelogic flow diagram 3200 shown in FIG. 53, case specific details forknowledge of tissue type are input 322 into the generator 500. The endeffector 125 of the surgical instrument 108 is closed on the tissue, asshown in FIGS. 42A-B, 43A-B, and the tissue coefficient of friction μ ischecked 3204 by the processor 502 and power is delivered 3206 to thetissue according to known normal force N, tissue coefficient of frictionμ, and tissue thickness as determined by processor 502 as describedherein. The processor 502 compares 3208 the rate of change of μ/|μ| toknown values of μ. In one aspect, a look-up table for predefined μ/PowerDelivery Ratios may be utilized by the processor 502. The processor 502adjusts 3210 the power delivered by the generator 500 higher or lowerbased on Δμ. When μ reaches 3212 a known or predetermined threshold, theprocessor 502 checks 3214 the clamp arm 145 of the end effector 125 forclosure against the ultrasonic blade 149. In one aspect, this can bedetermined based on known normal force N and known production normalforce N_(p) that represents a closed end effector jaw. When the jawclosure is complete, the processor 502 control the delivery 3216 ofshort bursts of power to complete the tissue transection or cut untilthe cut is completed 3218.

Accordingly, by measuring the tissue coefficient of friction μ, theprocessor 502 pulses to measure the tissue coefficient of friction μ atset time intervals and based on the measured coefficient μ over time,and adjusts the power delivered by generator 500 to the tissue in orderto transect or “cut” tissue efficiently and with good hemostasis. In oneaspect, the sensing technique monitors and periodically determines thetissue coefficient of friction μ, as described herein, while making thecut and modulates the energy delivered by the generator during the cutbased on change in the tissue coefficient of friction Δμ over time.

Techniques for Sealing or Sealing and Cutting Large Vessels andTissue-Bundles

In one aspect, the present disclosure provides a technique for sealingor sealing and cutting large vessels/tissue bundles by controlling thepower delivered to an end effector from a generator, such as any one ofthe generators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), or asurgical instrument, such as the surgical instrument 108 (FIGS. 1-3). Inaccordance with the resent technique, the power delivered to an endeffector of a surgical instrument can be varied based on the size ofvessels and tissue bundles interacting with the end effector. Forconciseness and clarity of disclosure, the techniques for sealing orsealing and cutting large vessels/tissue bundles will be described withreference to the multifunction surgical instrument 108 of FIG. 2 coupledto the generator 500 of FIG. 8, although it will be appreciated thatother configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

A technique for controlling the power output from a generator 500 thatis delivered to the end effector 125 of a surgical instrument 108 caninclude an input that represents a state of coagulation of the tissue toallow the energy profile from the generator 500 to be dynamicallychanged during the tissue treatment process between RF and ultrasonicenergy based on the state of coagulation of the tissue being treated bythe end effector 125 of the surgical instrument 108 or the size of thevessels or tissue interacting with the end effector 108. This allows theprocessor 502 to control the generator 500 to switch from RF energy(ENERGY2/RETURN) when a tissue seal is complete to ultrasonic energy(ENERGY1/RETURN) to cut the tissue and complete a procedure. Also, thistechnique allows the generator 500 to switch to ultrasonic energy at theinitial stages of treatment when either the vessel or tissue bundle istoo large to seal with RF energy alone. Thus, ultrasonic energy isapplied until the size of the vessel or tissue bundle is sufficientlyreduced to enable the RF to complete a proper seal. It will beappreciated that the switch between a first form of energy and a secondform of energy, and vice versa, can be done by first turning OFF thefirst form of energy and thereafter turning on the second form ofenergy. Alternatively, the switch between a first form of energy and asecond form of energy, and vice versa, can be done by transitioning fromthe first form of energy to the second form of energy, and vice versa,such that for brief period both the first and second forms of energy areturned ON simultaneously while one form ramps up and the other rampsdown. Thus, according to the latter approach, the RF and ultrasonicenergies can be blended during the transition rather than “one then theother” approach.

In one aspect, the present disclosure provides techniques to improve thecapability of the generator 500 to quickly and efficiently seal or sealand cut large vessels or large tissue bundles that present an initialextremely low impedance to the generator 500. These techniques shortentransaction times when sealing or sealing and cutting big tissue bundlesthat present low RF impedance to the generator 500. When RF energy isapplied to tissue with real low impedance, due to electrical currentcapacity limitations (maximum output current capability) of thegenerator 500, the maximum power that can be delivered into tissue islimited, which results in very long transaction cycles. Note that thecurrent limitation is not unique to the generators described herein andare applicable to other generators.

In one aspect, the state of coagulation of the tissue can be determinedusing a variety of techniques, In one aspect, the state of coagulationof the tissue is determined using a calculated tissue impedance andcomparing it to a threshold to find the termination impedance, asexplained above. The calculated tissue impedance, as described herein,is used by a technique to control the energy being delivered from thegenerator 500 to the surgical instrument 108.

In another aspect, the state of coagulation is determined using a“vector machine” or other techniques. In another aspect, the state ofcoagulation is determined using neural networks that are configured totake a plurality of factors into account. As discussed herein, a neuralnetwork refers to a series of techniques that attempt to identifyunderlying relationships in a set of data by using a process that mimicsthe way the human brain operates. Neural networks have the ability toadapt to changing input so that the network produces the best possibleresult without the need to redesign the output criteria. For example,the neural networks can take into account the tissue impedance asmeasured using the RF signal, the initial tissue impedance as measuredusing the RF signal, the energy that went into the transection, forexample, in joules, the transection time, the initial aperture of thejaw, the current aperture of the jaw, and/or the rate of change of thetissue impedance. One example of a neural network 5500 for controlling agenerator is described hereinbelow in connection with FIG. 82.

FIG. 54 is a logic flow diagram 3300 of one aspect of a process forsealing or sealing and cutting large vessels or large tissue bundles. Asdescribed herein, the logic flow diagram 3300 may be implemented in thegenerator 500, the multifunction surgical instrument 108, or acombination thereof. With reference now to the logic flow diagram 3300shown in FIG. 54 and the surgical system 10 of FIG. 1, the state ofcoagulation of the tissue is determined as described herein. Thegenerator 500 is configured to deliver RF energy (ENERGY2/RETURN) andultrasonic energy (ENERGY1/RETURN) to switch between the RF andultrasonic energy according to various techniques. The end effector 125of the surgical instrument 108 is advanced and the tissue is clamped3302 between the clamp arm 145 and the ultrasonic blade 149. The endeffector 125 is activated with RF energy from the generator 500 and RFenergy is delivered 3304 to the tissue to effect a seal employing aprocess such as a composite load curve (CLC) control process describedin connection with the logic diagram 5400 shown FIG. 81. With referenceback to FIG. 54, the processor 502 determines 3306 the state ofcoagulation to determine if a state of completion of coagulation of thetissue has been achieved, at which time the processor 502 signals thewaveform generator 504 and amplifier 506 to switch from RF energy forcoagulating tissue to ultrasonic energy for cutting tissue. If thedesired tissue of coagulation or seal has not been achieved, theprocessor 502 continues along the NO branch and RF energy is continuedto be delivered. When the proper state of coagulation has been reached,the processor 502 continues along the YES branch and the RF energy isswitched 3308 to ultrasonic energy to cut the tissue. The tissue isreleased 3310 from the end effector 215 once the tissue cut is completedwith the ultrasonic energy.

Also disclosed herein are techniques for dynamically changing the energydelivered from a generator based on end effector aperture. According toone aspect, a technique for controlling the power output from agenerator, such as the generator 500 of FIG. 8, that is delivered to theend effector of a surgical instrument, such as surgical instrument 108(FIGS. 1-3) can include an input that represents the aperture of the endeffector 125 of the surgical instrument 108. The energy profile from thegenerator 500 can be dynamically changed during the procedure between RFand ultrasonic energy based on the size of the aperture defined by theend effector 125 clamping the tissue. This allows the generator 500 toswitch from RF energy to ultrasonic energy based on the amount that theend effector 125 is clamping on the tissue being treated by the surgicalinstrument 108. The aperture of the clamp arm 145 is related to thecreation of a proper coagulation seal, for example, when RF energy isdelivered from the generator 500 to the end effector 125 of the surgicalinstrument 108, such that RF energy is used when there is sufficientclosure of the end effector 125 on the tissue. Thus, if the aperturedefined by the end effector is too large and there is insufficient clampon the tissue for proper coagulation, only ultrasonic energy isdelivered to the end effector 125.

For example, false information regarding various tissue measurementsand/or characteristics can be transmitted to the generator 500 forcontrolling the energy delivered depending on the aperture defined bythe end effector 125. One such measurement that can be affected by theaperture defined by the end effector 125 is tissue impedance. Anincorrect tissue impedance determination can lead to early terminationof a coagulation “sealing” cycle as the generator 500 may switch from RFto ultrasonic energy before a proper coagulation seal has been achieved.

The aperture defined by the end effector 125 can be determined using avariety of techniques. In one form, the aperture defined by the endeffector 125 is determined by detecting the pivot angle of the endeffector 125. This can be accomplished using a potentiometer, a Halleffect sensor, an optical encoder, an optical IR sensor, an inductancesensor, or a combination thereof. In another form, the proximity offirst and second components of an end effector 125 is measured todetermine the aperture defined by the end effector 125 using, forexample, a Hall effect sensor, an optical IR, inductance sensor, orcombination thereof. In another form, a surgical instrument 125 isconfigured to detect the aperture defined by the end effector 125 bymeasuring a change in a tissue impedance of the tissue interacting withthe end effector 125. In another form, a surgical instrument isconfigured to detect the aperture defined by the end effector 125 bymeasuring a load applied by the end effector 125 on the tissue asultrasonic energy is pulsed to the end effector 125. In another form,the surgical instrument includes a switch or other mechanism for closingthe end effector 125 that can detect the aperture defined by the endeffector 125. As previously discussed, the tissue impedance isdetermined by the processor 502 by dividing the voltage applied to theend effector 125 by the current delivered to the end effector 125. Forexample, the processor 502 can determine the tissue impedance bydividing the voltage sensed by the second voltage sensing circuit 524 bythe current sensed by the current sensing circuit 514.

FIG. 55 is a logic flow diagram 3400 of one aspect of a process forsealing or sealing and cutting large vessels or large tissue bundles bydynamically changing energy being delivered from the generator 500during the treatment of the tissue based on the changing aperturedefined by the end effector. As described herein, the logic flow diagram3400 may be implemented in the generator 500, the multifunction surgicalinstrument 108, or a combination thereof. With reference now to thelogic flow diagram 3400 shown in FIG. 55, the processor 502 determinesthe aperture defined by the end effector 125 as described above. Theprocessor 502 then determines the state of coagulation of the tissue asdescribed herein. The generator 500 or the surgical instrument 108 maybe configured to deliver RF energy (ENERGY2/RETURN) and ultrasonicenergy (ENERGY1/RETURN) to switch between the RF and ultrasonic energyaccording to various techniques. The end effector 125 of the surgicalinstrument 108 is advanced and the tissue and the end effector 125 ofthe surgical instrument 108 is closed 3402 on tissue and the endeffector 125 is activated with energy from the generator 500. Theprocessor 502 determines 3404 the aperture defined by the end effector125 using any of the techniques described above. The processor 502signals the energy delivered from the generator 500 to the end effector125 and controls when the generator 500 switches between RF andultrasonic energy based on the aperture defined by the end effector 125.Accordingly, the processor 502 selects 3406 the generator 500 powerdelivery profile based on the aperture defined by the end effector 125.The processor 502 monitors 3408 the aperture defined by the end effector125 during the tissue treatment process to dynamically change 3410 theenergy delivered from the generator 500 during the tissue treatmentprocess based on the changing aperture defined by the end effector 125.

In another aspect, a technique for controlling the power delivered fromthe generator 500 to the end effector 125 of the surgical instrument 108can include an input that includes energy parameters based on anaperture of the end effector 125 of the surgical instrument 108. Duringthe tissue treatment process, the processor 502 can dynamically changethe energy output profile of the generator 500 between RF energy andultrasonic energy using energy parameters based on the aperture definedby the end effector 125 clamping the tissue. This allows the generator500 to switch from RF energy to ultrasonic energy based on how muchclamping force the end effector is applying to the tissue during thetreatment process. As explained above, the aperture of the clamp arm 145is related to creating a proper coagulation seal. For example, RF energyshould be delivered by the generator 500 to the end effector 125 onlywhen there is sufficient closure of the end effector 125 on the tissue.Thus, when the aperture defined by the end effector 125 is too large andthere is insufficient clamping force on the tissue for propercoagulation, only ultrasonic energy should be delivered to the endeffector 125.

The aperture defined by the end effector 125 can be determined using anyof the methods described above. For example, the surgical instrument 108can include an aperture sensor in the end effector 125 that can be fedthrough a connector to the ASIC in the handle 109 of the surgicalinstrument 108. The surgical instrument 108 also can include a sensor inthe handle 109 of the surgical instrument 108 that is configured todetect the aperture defined by the end effector 125.

Energy parameters are configured to be loaded into the generator 500,and can include a plurality of different parameters, including but notlimited to voltage, current, power, and one or more techniques for usein treating tissue. These parameters can be related to the RF energy andultrasonic energy that can be delivered from the generator 500. Theenergy parameters can include information such as maximum and/or minimumvalues to be used to control the energy delivered from the generator500. The energy parameters can be stored in a variety of locations,including an EEPROM on the surgical instrument 108 or some othernon-volatile memory. In addition, there can be multiple sets of energyparameters. For example, the processor 502 can use a first set of energyparameters to optimize tissue transection, and a second set of energyparameters to optimize tissue spot coagulation. It will be understoodthat there can be any number of set of energy parameters that correspondto various types of tissue treatments to allow the generator 500 toswitch between the various sets of energy parameters based on thenecessary tissue treatments.

When the end effector 125 of the surgical instrument 108 is activated,the processor 502 utilizes the various techniques described above todetect the aperture defined by the end effector 125. In one aspect, whenthe end effector 125 is closed around the tissue, the generator 500 canutilize the energy parameters for optimizing tissue transection. Whenthe end effector 125 has a larger aperture and is not clamped on thetissue, the generator 500 can utilize the energy parameters foroptimizing spot coagulation of the tissue.

FIG. 56 is a logic flow diagram 3500 of one aspect of a process forsealing or sealing and cutting large vessels or large tissue bundles bydynamically communicating energy parameters to the generator 500 duringthe tissue treatment process based on the changing aperture defined bythe end effector 125 of the surgical instrument 108. As describedherein, the logic flow diagram 3500 may be implemented in the generator500, the multifunction surgical instrument 108, or a combinationthereof. With reference now to the logic flow diagram 3500 shown in FIG.56, the processor 502 determines the aperture defined by the endeffector 125 as described above. The generator 500 is configured todeliver RF energy (ENERGY2/RETURN) and ultrasonic energy(ENERGY1/RETURN) and to switch between the RF and ultrasonic energyaccording to various techniques. The end effector 125 of the surgicalinstrument 108 is advanced, the end effector 125 of the surgicalinstrument 108 is closed 3502 on the tissue. and the end effector 125 isactivated with energy from the generator 500. The processor 502determines 3504 the aperture defined by the end effector 125 using anyof the techniques described above. The processor 502 signals the energydelivered from the generator 500 and to switch between RF and ultrasonicenergy based on the aperture defined by the end effector 125 based onsets of energy parameters previously loaded into the generator 500.Accordingly, energy parameters are communicated 3506 to the generator500 based on the measured aperture defined by the end effector 125. Theaperture defined by the end effector 125 is monitored 3508 during thetissue treatment process such that the energy delivered from thegenerator 500 can be dynamically changed during the tissue treatmentprocess based on the changing aperture defined by the end effector 125.Accordingly, the processor 502 dynamically communicates 3510 energyparameters to the generator 500 based on the measured aperture definedby the end effector 125. This allows the generator 500 to dynamicallyswitch between various sets of energy parameters based on the changingaperture defined by the end effector 125.

It will be understood that various combinations of information can beused to determine which set of energy parameters are to be used duringthe tissue treatment process. For example, the aperture defined by theend effector 125 and calculated tissue impedance can be used by theprocessor 502 to determine which set of energy parameters are needed tocontrol the energy being delivered from the generator 500. As previouslydiscussed, the tissue impedance is determined by the processor 502 bydividing the voltage applied to the end effector 125 by the currentdelivered to the end effector 125. For example, the processor 502 candetermine the tissue impedance by dividing the voltage sensed by thesecond voltage sensing circuit 524 by the current sensed by the currentsensing circuit 514.

In another aspect, a technique for controlling the power output from thegenerator 500 and delivered to the end effector 125 of the surgicalinstrument 108 can include an input that includes inputs related to thesize of the tissue being treated by the end effector 125 of the surgicalinstrument 108. During the tissue treatment process, the processor 502dynamically changes the energy delivered from the generator 500 betweenRF energy and ultrasonic energy to achieve dissection and coagulation oflarge vessels and large tissue bundles based on a determination of theeffectiveness of the RF energy in coagulating the large vessels or largetissue bundles. A determination of the effectiveness of the RF energy incoagulating a tissue includes a calculation of tissue impedance, asexplained above, of the large tissue interacting with the end effector125, which is used to determine the type of energy delivered by thegenerator 500 to the end effector 125.

FIG. 57 is a logic flow diagram 3600 of a technique to seal or seal andcut vessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements and the aperture defined by the clamp armmeasurements. As described herein, the logic flow diagram 3600 may beimplemented in the generator 500, the multifunction surgical instrument108, or a combination thereof. With reference now to the logic flowdiagram 3600 shown in FIG. 57, the end effector 125 is advanced and theclamp arm 145 is closed 3602 on tissue located between the clamp arm 145and the ultrasonic blade 149 of the end effector 125. The end effector125 is then activated with RF energy (ENERGY2/RETURN) from the generator500 to form a seal. The processor 502 determines 3604 the tissueimpedance and the aperture defined by the end effector 125 as describedherein. As previously discussed, the tissue impedance is determined bythe processor 502 by dividing the voltage applied to the end effector125 by the current delivered to the end effector 125. For example, theprocessor 502 can determine the tissue impedance by dividing the voltagesensed by the second voltage sensing circuit 524 by the current sensedby the current sensing circuit 514.

The aperture defined by the end effector 125 and the processor 502determines 3604 the tissue impedance using any of the techniquesdescribed herein. The processor 502 compares 3606 the tissue impedancevalues to stored threshold values and determines 3608 whether or notthese values are greater than the threshold values. If either the tissueimpedance or the aperture defined by the end effector 125 is less thanthe threshold value, the processor 502 continuous along the NO branchand RF energy (ENERGY2/RETURN) continues to be delivered from thegenerator 500 to the end effector 125. If the tissue impedance and theaperture defined by the end effector 125 are greater than the thresholdvalue, the processor 502 continues along the YES branch and switches3610 the to delivering ultrasonic energy (ENERGY1/RETURN) from thegenerator 500. This allows the large vessels and large tissue bundles tobe reduced in size or shrunk with ultrasonic energy to a size that wouldallow the RF energy to form a more optimal seal.

The processor 502 determines 3612 the aperture defined by the endeffector 125 using any of the techniques described herein. The processor502 then compares 3614 these aperture values to stored thresholdaperture values and determines whether or not these aperture valuesrepresent that the tissue has been shrunk by the ultrasonic energy to asize that would allow the RF energy to properly seal the tissue. If theprocessor 502 determines that tissue is too large for RF energy sealing,the processor 502 continues along the NO branch and ultrasonic energycontinues to be delivered from the generator 500 to the end effector 125to continue shrinking the tissue. If the processor 502 determines thatthe tissue is has been shrunk to an appropriate size suitable forsealing with RF energy, the processor 502 continues along the YES branchand switches 3616 the energy delivered from the generator 500 to RFenergy. The processor 502 signals can optionally switch back 3618 todelivering ultrasonic energy upon determining that the RF energy hascompleted the tissue seal.

FIG. 58 is a logic flow diagram 3700 of one aspect of a process forsealing or sealing and cutting large vessels or large tissue bundles. Asdescribed herein, the logic flow diagram 3700 may be implemented in thegenerator 500, the multifunction surgical instrument 108, or acombination thereof. With reference now to the logic flow diagram 3700shown in FIG. 58, tissue is initially grasped 3702 by the end effector125 between the clamp arm 145 and the ultrasonic blade 149. RF energy(ENERGY2/RETURN) is delivered 3704 to the end effector 125. Theprocessor 502 monitors 3706 the tissue impedance Z_(T) and jaw apertureA_(j) for a predetermined period T_(o), which may be selected from arange of 0.5 to 2.0 seconds, and preferably about 1.5 seconds, forexample. As previously discussed, the tissue impedance is determined bythe processor 502 by dividing the voltage applied to the end effector125 by the current delivered to the end effector 125. For example, theprocessor 502 can determine the tissue impedance by dividing the voltagesensed by the second voltage sensing circuit 524 by the current sensedby the current sensing circuit 514.

Until the predetermined period T_(o) elapses 3708, the processor 502continues along the NO branch and the generator 500 continues to deliverRF energy and the processor 502 continues to monitor (measure) tissueimpedance Z_(T) and jaw aperture A_(j). At the end of the time periodT_(o), if tissue impedance Z_(T) has not increased to a value equal toor greater than a predetermined threshold and the jaw aperture is equalto or less than a predetermined threshold, the processor 502 proceedsalong the YES branch and switches 3710 the generator 500 to ultrasonicenergy mode. Ultrasonic energy is delivered 3712 to the tissue while theprocessor 502 monitors the tissue impedance Z_(T) and jaw aperture A_(j)until the tissue shrinks to a size that is suitable for sealing with RFenergy. The processor 502 compares 3714 the jaw aperture A_(j) to athreshold jaw aperture and if it is less than or equal to the thresholdthe processor 502 continues along the YES branch assuming that thetissue is sized for sealing by RF energy. The processor 502 switches thegenerator 500 to RF energy mode and delivers 3716 RF energy to completethe seal while the processor 502 monitors the tissue impedance Z_(T) todetermine 3718 if the seal is complete. If the seal is complete andseal-only is desired, the processor 502 completes 3720 the operation. Ifthe seal is complete and seal and cut is desired, the processor 502switches the generator 500 to ultrasonic energy mode and delivers 3722ultrasonic energy to cut the sealed tissue. Upon cutting the tissue, theprocessor 502 completes 3720 the operation.

FIG. 59 is a logic flow diagram 3800 of a technique to seal or seal andcut vessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements. As described herein, the logic flow diagram 3800may be implemented in the generator 500, the multifunction surgicalinstrument 108, or a combination thereof. With reference now to thelogic flow diagram 3800 shown in FIG. 59, tissue is clamped between theclamp arm 145 and the ultrasonic blade 149 of the end effector 125 ofthe surgical instrument 108. The processor 502 signals the waveformgenerator 504 and amplifier 506 to deliver 3802 RF energy(ENERGY2/RETURN) to the end effector 125 of the surgical instrument 108interacting with tissue to create a tissue seal using the RF energy. Theprocessor 502 calculates 3804 a first tissue impedance Z_(T1) of thetissue interacting with the end effector 125 at the start of the periodT_(o) of the delivery of the RF energy and then calculates 3806 a secondtissue impedance Z_(T2) of the tissue interacting with the end effectorafter the RF energy is delivered for a predetermined period T₁. Aspreviously discussed, the tissue impedance is determined by theprocessor 502 by dividing the voltage applied to the end effector 125 bythe current delivered to the end effector 125. For example, theprocessor 502 can determine the tissue impedance by dividing the voltagesensed by the second voltage sensing circuit 524 by the current sensedby the current sensing circuit 514.

The processor 502 compares Z_(T1) to Z_(T2). If Z_(T2) is less than orequal to Z_(T1) after RF energy is delivered for a period of T₁, theremay be a short circuit or the tissue impedance is too low for RF energyto deliver power to the tissue. Accordingly, the processor 502 proceedsalong the YES branch and controls the waveform generator 504 andamplifier 506 to stop 3810 delivering RF energy to the end effector 125and start delivering 3812 ultrasonic energy to the end effector 125until Z_(T2) is greater than Z_(T1). Once Z_(T2) exceeds Z_(T1), theprocessor 502 continues along the NO branch and controls the waveformgenerator 504 and amplifier 506 to continue 3814 delivering RF energy tothe end effector 125 until the tissue is sealed 3816. Once the tissue issealed, the processor 502 continues along the YES branch and thecontrols the waveform generator 504 and amplifier 506 to stop deliveringRF energy to the end effector 125 and to start delivering 3820ultrasonic energy to cut the tissue. If the tissue is not sealed, theprocessor 502 continues along the NO branch and the generator 500continues delivering RF energy to the end effector until the tissue sealis completed.

In another aspect, a technique for controlling the power output from thegenerator 500 delivered to the end effector 125 of the surgicalinstrument 108 can include an input that includes inputs related to thesize of the tissue being treated by the end effector 125 of the surgicalinstrument 108. The energy delivered from the generator 500 can bedynamically changed during the procedure between RF and ultrasonicenergy to achieve dissection and coagulation of a large tissue based ona determination of the effectiveness of the RF energy in coagulating thelarge tissue. A determination of the effectiveness of the RF energy incoagulating a tissue includes a calculation of tissue impedance, asexplained above, of the large tissue interacting with the end effector125, which is used to determine the type of energy being delivered bythe generator 500 to the end effector 125.

FIG. 60 is a logic flow diagram 3900 of a technique to seal or seal andcut vessels using RF and ultrasonic energy in conjunction with tissueimpedance measurements and the aperture defined by the clamp jawmeasurements. As described herein, the logic flow diagram 3900 may beimplemented in the generator 500, the multifunction surgical instrument108, or a combination thereof. With reference now to the logic flowdiagram 3900 shown in FIG. 60, tissue is clamped between the clamp arm145 and the ultrasonic blade 149 of the end effector 125 of the surgicalinstrument 108. The processor 502 signals the waveform generator 504 andamplifier 506 to deliver 3902 RF energy (ENERGY2/RETURN) to the endeffector 125 of the surgical instrument 108 interacting with tissue tocreate a tissue seal using the RF energy. The processor 502 calculates3904 a first tissue impedance Z_(T1) of the tissue interacting with theend effector 125 at the start of a period T_(o) of delivery of the RFenergy and then calculates 3906 a second tissue impedance Z_(T2) of thetissue interacting with the end effector 125 after the RF energy isdelivered for a predetermined period T₁ and measures the aperture A_(j)defined by the clamp arm 145. As previously discussed, the tissueimpedance is determined by the processor 502 by dividing the voltageapplied to the end effector 125 by the current delivered to the endeffector 125. For example, the processor 502 can determine the tissueimpedance by dividing the voltage sensed by the second voltage sensingcircuit 524 by the current sensed by the current sensing circuit 514.

The processor 502 compares Z_(T1) to Z_(T2). If Z_(T2) is less than orequal to Z_(T1) after RF energy is delivered for a period of T₁, theprocessor 502 determines that there may be a short circuit or extremelylow the tissue impedance present at the end effector 125 that is too lowfor RF energy to deliver any power to the tissue. Accordingly, theprocessor 502 proceeds along the YES branch and the generator 500 andcompares the measured aperture A_(j) defined by the clamp arm 145 to apredetermined threshold aperture A_(jo) defined by the clamp arm 145,where the predetermined threshold aperture A_(jo) d corresponds to athick vessel or a thick tissue bundle located between the clamp arm 145and the ultrasonic blade 149. If the measured aperture A_(j) defined bythe clamp arm 145 is less than or equal to the predetermined thresholdaperture A_(jo), the processor 502 continues along the NO branch andcontrols the waveform generator 504 and amplifier 506 to continuedelivering RF energy to the end effector 125 until the tissue impedanceZ_(T2) is less than the initial tissue impedance Z_(T1). If the measuredaperture A_(j) defined by the clamp arm 145 is greater than thepredetermined threshold aperture A_(jo), the processor 502 continuesalong the YES branch and controls the generator to stop 3110 deliveringRF energy to the end effector 125 and start delivering 3112 ultrasonicenergy (ENERGY1/RETURN) to the end effector 125 until Z_(T2) is greaterthan Z_(T1). Once Z_(T2) is greater than Z_(T1), the processor 502continues along the NO branch and controls the waveform generator 504and amplifier 506 to continue 3114 delivering RF energy to the endeffector 125 until the tissue is sealed 3116. Once the tissue is sealed,the processor 502 continues along the YES branch and controls thewaveform generator 504 and amplifier 506 to stop delivering RF energyand start delivering 3920 ultrasonic energy to the end effector 125 tocut the tissue. If the tissue is not sealed, the processor 502 continuesalong the NO branch and controls the waveform generator 504 andamplifier 506 to continue delivering RF energy to the end effector 125until the tissue seal is complete.

Techniques for Switching Between RF and Ultrasonic Energy Based on theState of Coagulation of Tissue

In one aspect, the present disclosure provides a technique for switchingbetween RF and ultrasonic energy based on the state of coagulation oftissue by controlling the power delivered to an end effector from agenerator, such as any one of the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), or a surgical instrument, such as the surgicalinstrument 108 (FIGS. 1-3). In accordance with the present technique,the power delivered to an end effector of a surgical instrument can beswitched between RF and ultrasonic based on the state of coagulation oftissue interacting with the end effector. For conciseness and clarity ofdisclosure, the techniques for switching between RF and ultrasonicenergy based on the state of coagulation of tissue will be describedwith reference to the multifunction surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

To address these issues, in some aspects, a generator 500 capable ofhandling both ultrasonic and RF electrosurgical systems may include acompletely nested neural network to identify whether the generator 500is presented with a true short circuit vs. a low impedance tissue. Inaddition, in some aspects, to assist in the detection of short circuits,the neural network may be configured to track and store at least thefollowing factors: a. Measured resistance/impedance; b. Drive current(RMS); c. Drive Voltage (RMS); and d. Moving average of measuredimpedance. In some aspects, the neural network will be thought to inorder to be capable of discerning between a true short and low impedancetissue.

Furthermore, in some aspects, methods for detecting a short circuit mayutilize the ultrasonic functionality to cut low impedance tissue and toidentify a true short circuit. For example, instead of faulting, thegenerator 500 may send in an exploratory pulse to the ultrasonictransducer 120. The tissue properties initially assessed by theultrasonic blade 149 touching a metal short would result in a higheroutput drive voltage and resulting impedance. This level of impedancemay be measured to determine whether the material was actually metalversus low impedance tissue. If the processor 502 determines that metalis not present in the end effector 125, the generator 500 continues todeliver ultrasonic energy to the end effector 125 and cut through theload. Thus, if the impedance is too low for the application of RF energyto seal the tissue in a timely manner, ultrasonic energy could beapplied cut through non-metal low impedances without difficulty.

FIG. 61 is a logic flow diagram 4000 of one aspect of a technique fordistinguishing a short circuit from low impedance tissue while utilizingRF energy by measuring voltage properties of an exploratory ultrasonicpulse. As described herein, the logic flow diagram 4000 may beimplemented in the generator 500, the multifunction surgical instrument108, or a combination thereof. With reference now to FIG. 61, the logicflow diagram 4000 provides a method for distinguishing a short circuitfrom low impedance tissue. With reference to the surgical instrument 108of FIG. 2 coupled to the generator 500 of FIG. 8, tissue is clampedbetween the clamp arm 145 and the ultrasonic blade 149 of the endeffector 125 of the surgical instrument 108. In accordance with themethod, the processor 502 signals the waveform generator 504 andamplifier 506 to transition 4002 from delivering RF energy(ENERGY2/RETURN) to delivering ultrasonic energy (ENERGY1/RETURN). Theprocessor 502 then controls the waveform generator 504 and amplifier 506to transmit 4004 an exploratory pulse to the ultrasonic transducer 120to apply ultrasonic energy to the short circuit area in question. Theprocessor 502 then measures 4006 the output drive voltage and drivecurrent and determines the impedance. As previously discussed, thetissue impedance is determined by the processor 502 by dividing thevoltage applied to the end effector 125 by the current delivered to theend effector 125. For example, the processor 502 can determine thetissue impedance by dividing the voltage sensed by the second voltagesensing circuit 524 by the current sensed by the current sensing circuit514. At this juncture, the processor 502 determines 4008 whether theimpedance is consistent with low impedance tissue. When the impedance isconsistent with low impedance tissue, the processor 502 proceeds alongthe YES branch and controls the waveform generator 504 and amplifier 506to continue 4010 delivering ultrasonic energy to cut through tissue.When the impedance is not consistent with low impedance tissue, theprocessor 502 proceeds along the NO branch and controls the waveformgenerator 504 and amplifier 506 to stop 4012 the application ofultrasonic energy.

Additionally, in some aspects, if a short is detected while in RF modeand delivering RF energy to the end effector 125, the processor 502signals the waveform generator 504 and amplifier 506 to transmit anultrasonic pulse to the ultrasonic transducer 120. A microphone andultrasonic application can be configured to detect the sound ofcharacteristic ultrasonic vibrations against metal, since it would bevery apparent and instantly or easily recognizable. Using knowledge inacoustics and waveform engineering, the processor 502 can account forwhat frequencies are heard due to the ultrasonic blade 149 acting onmetal and on other non-tissue materials.

FIG. 62 is a logic flow diagram 4100 of a technique for distinguishing ashort circuit from low impedance tissue while delivering RF energy andmeasuring acoustic properties of an exploratory ultrasonic pulse,according to some aspects. As described herein, the logic flow diagram4100 may be implemented in the generator 500, the multifunction surgicalinstrument 108, or a combination thereof. With reference now to FIG. 62,the logic flow diagram 4100 provides a method for distinguishing a shortcircuit from low impedance tissue. The tissue is clamped between theclamp arm 145 and the ultrasonic blade 149 of the end effector 125 ofthe surgical instrument 108. In accordance with the method, theprocessor 502 signals the waveform generator 504 and amplifier 506 totransition 4102 from delivering RF energy (ENERGY2/RETURN) to deliveringultrasonic energy (ENERGY1/RETURN). The processor 502 then controls thewaveform generator 504 and amplifier 506 to transmit 4104 an exploratorypulse to the ultrasonic transducer 120 to apply ultrasonic energy to theshort circuit area in question. The processor 502 measures 4106 theacoustic properties of the area in question based on applied ultrasonicvibrations. At this juncture, the processor 502 determines 4108 whetherthe acoustic properties are consistent with the low impedance tissue.When the processor 502 determines acoustic properties are consistentwith low impedance tissue, the processor 502 proceeds along the YESbranch and controls the waveform generator 504 and amplifier 506 tocontinue 3210 delivering ultrasonic energy to cut through tissue. Whenthe processor 502 determines that the acoustic properties are consistentwith low impedance tissue, the processor 502 proceeds along the NObranch and controls the waveform generator 504 and amplifier 506 to stop4112 delivering ultrasonic energy.

In some aspects, a neural network, such as neural network 5500 forcontrolling a generator shown in FIG. 82, may be programmed to identifythese properties in metal, tissues, and other non-tissue materials. Theneural network also may be configured to transmit the exploratory pulseto the ultrasonic transducer. In addition, new developments oradditional programs, including receiving feedback from the attempts todetect short circuits, may be incorporated back into the neural networkto increase its situational awareness and effectively better learn howto detect a true short circuit. With confirmation of a short circuitboth by RF and ultrasonic functionality, this can allow for less timespent getting repeat errors on RF and faster transection on lowimpedance tissue.

Also disclosed herein are techniques for combining RF energy andultrasonic energy to seal tissue without cutting. In some aspects, thesurgical system including the generator of the present disclosures maybe configured to implement a method for sealing tissue at a surgicalsite without cutting, by using a combination of ultrasonic energy and RFenergy. In some aspects, the method includes superimposing theultrasonic drive signal together with a fixed low RF signal (e.g.,ultrasonic at 55.5 KHz and RF at 330 KHz). For example, during a sealingprocedure, the ultrasonic drive signal may be configured to dynamicallychange in order to: (1) track the resonance of the ultrasonic drivesignal, and (2) provide the desired strength or amplitude of vibrationsin order to achieve the desired tissue effect. The fixed low RF signalwill be provided in order to measure the tissue impedance and modify theultrasonic drive to achieve the desired seal without cutting.

The RF signal may be superimposed in several non-exhaustive ways. In oneway, the RF drive signal may be superimpose on top of the ultrasonicdrive signal in a continuous fashion. In another way, the ultrasonicdrive signal may be time sliced in such way that periodically oraperiodically, e.g., every 250 mSec, the ultrasonic drive signal willcease and a short burst of the RF drive signal of, e.g., 50 mSec, willbe driving the output at a sub-therapeutic level which will still besufficient to measure tissue impedance. After this burst, the processor502 will control the waveform generator 504 and the amplifier 506 toswitch the output of the generator 500 back to delivering the ultrasonicdrive signal. The overall control loop may be configured to monitor theRF tissue impedance and adjust the ultrasonic drive signal output toachieve a tissue seal without cutting the tissue.

FIG. 63 is a logic flow diagram 4200 of a technique for conducting atissue sealing technique without cutting by using a combination ofultrasonic energy and RF energy, according to some aspects. As describedherein, the logic flow diagram 4200 may be implemented in the generator500, the multifunction surgical instrument 108, or a combinationthereof. With reference now to FIG. 63, the logic flow diagram 4200provides an example iterative technique for cyclically combining RFenergy (ENERGY2/RETURN) and ultrasonic energy (ENERGY1/RETURN) to sealtissue without cutting, according to some aspects. Tissue is clampedbetween the clamp arm 145 and the ultrasonic blade 149 of the endeffector 125 of the surgical instrument 108. In accordance with themethod, the processor 502 signals the waveform generator 504 to deliver4202 an ultrasonic drive signal during a first interval of time to sealtissue at a surgical site. The processor 502 then controls the waveformgenerator 504 and the amplifier 506 to cease 4204 the ultrasonic drivesignal after the first interval. The processor 502 then controls thewaveform generator 504 and the amplifier 506 to deliver an RF drivesignal at a sub-therapeutic amplitude during a second interval of timeto measure tissue impedance. The processor 502 then controls thewaveform generator 504 and the amplifier 506 to cease 4208 the RF drivesignal after the second interval of time. The processor 502 then adjusts4210 an ultrasonic drive signal based on the measured impedance from theRF drive signal. The processor 502 repeats 4212 the procedure until thesurgical site is sealed.

The input to this control system to reduce/modify the ultrasonic drivesignal and at eventually completely terminate the ultrasonic drivesignal can utilize the following non-exhaustive methods: follow a powerreduction and termination technique based on regular logic, fuzzy logic,vector machine, or neural network utilizing the following example:initial tissue impedance, initial jaws-aperture, current tissueimpedance, rate of change of tissue impedance, energy driven intotissue, and transection time.

In some aspects, the surgical system may be configured to measure theseterms through one or more sensors. Example methods for monitoring theseterms and the ultrasonic functionality of the combination RF andultrasonic surgical system may be based on methods described in U.S.Pat. No. 9,017,326, titled “Impedance Monitoring Apparatus, System, AndMethod For Ultrasonic Surgical Instruments,” which is herebyincorporated by reference in its entirety.

FIG. 64 is a logic flow diagram 4300 of a technique for conducting atissue sealing technique without cutting by using a combination ofultrasonic energy and RF energy, according to some aspects. As describedherein, the logic flow diagram 4300 may be implemented in the generator500, the multifunction surgical instrument 108, or a combinationthereof. With reference now to FIG. 64, the logic flow diagram 4300provides an example iterative technique for cyclically combining RFenergy (ENERGY2/RETURN) and ultrasonic energy (ENERGY1/RETURN) to sealtissue without cutting, according to some aspects. Tissue is clampedbetween the clamp arm 145 and the ultrasonic blade 149 of the endeffector 125 of the surgical instrument 108. In accordance with themethod, the processor 502 signals the waveform generator 504 to deliver4302 an ultrasonic drive signal to the tissue during a first interval oftime T₁. The processor 502 then controls the waveform generator 504 andthe amplifier 506 to cease 4304 the ultrasonic drive signal after thefirst interval T₁. The processor 502 then controls the waveformgenerator 504 and the amplifier 506 to deliver 4306 an RF drive signalat a sub-therapeutic amplitude during a second interval T₁ of time tomeasure the tissue impedance. The processor 502 then controls thewaveform generator 504 and the amplifier 506 to cease 4308 the RF drivesignal after the second time interval T₂. The processor 502 thencontrols the waveform generator 504 and the amplifier 506 to iterativelyadjust 4310 the ultrasonic drive signal based on the measured tissueimpedance until the processor 502 determines that the tissue is sealed.As previously discussed, the tissue impedance is determined by theprocessor 502 by dividing the voltage applied to the end effector 125 bythe current delivered to the end effector 125. For example, theprocessor 502 can determine the tissue impedance by dividing the voltagesensed by the second voltage sensing circuit 524 by the current sensedby the current sensing circuit 514.

Techniques for Improving Short Circuit Detection in a CombinationUltrasonic/RF Surgical Instrument

In one aspect, the present disclosure provides a technique for detectingextremely low impedances or actual short circuits in the end effector bycontrolling the power delivered to an end effector from a generator,such as any one of the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and4-8), or a surgical instrument, such as the surgical instrument 108(FIGS. 1-3). In accordance with the present technique, the powerdelivered to an end effector of a surgical instrument can be variedbased on whether a very low impedance or actual short circuit conditionis present at the end effector. For conciseness and clarity ofdisclosure, the techniques for detecting extremely low impedances oractual short circuits in the end effector will be described withreference to the multifunction surgical instrument 108 of FIG. 2 coupledto the generator 500 of FIG. 8, although it will be appreciated thatother configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

Disclosed herein are techniques for detecting short circuits, includingimplementing detection methods in a neural network. In some aspects, theultrasonic generator 500 of the present disclosures includes componentsconfigured to accurately and reliably detect short circuits.Particularly when performing surgeries on body tissue typical with useof the end effectors described herein, detecting a short circuit can bedifficult for a number of reasons. For example, many times tissuepresents itself as a short circuit, thereby fooling the detectionsoftware and at low signal magnitudes, which are inherent when drivingsignals with a short circuit, the measurement(s) error(s) is/aresubstantial and can result in making the wrong decision whether thegenerator is presented with a true short circuit. In addition, in someaspects of the generator described herein, low impedance tissue or metalshorts cause the generator to fault while in RF mode. In general, it maybe difficult for the generator to distinguish between low impedancetissue and metal, where one may result in a true short circuit while theother is merely based on low impedance tissue.

FIG. 65 is logic flow diagram 4400 of a technique for detecting lowimpedance tissue or metal shorts that may cause false short circuits inRF mode. As described herein, the logic flow diagram 4400 may beimplemented in the generator 500, the multifunction surgical instrument108, or a combination thereof. With reference now to FIG. 65, the logicflow diagram 4400 provides an example technique for detecting lowimpedance tissue or metal shorts that may cause false short circuits inRF mode. Tissue is clamped between the clamp arm 145 and the ultrasonicblade 149 of the end effector 125 of the surgical instrument 108. Inaccordance with the method, if the processor 502 cannot distinguish lowimpedance tissue from metal located between the clamp arm 145 and theultrasonic blade 149 of the end effector 125, the processor 502 signalsthe waveform generator 504 to deliver ultrasonic energy (ENRGY1/RETURN)to cut low impedance tissue and to identify a true short circuit, suchas metal to metal contact between the clamp arm 145 and the ultrasonicblade 149. In accordance with the method, the processor 502 signals thewaveform generator 504 to deliver 4402 RF energy (ENERGY2/RETURN) withthe end effector 125 to the target surgical site. The processor 502 thencontrols the waveform generator 504 and the amplifier 506 to transition4404 from delivering RF energy to delivering ultrasonic energy to theend effector 125. The processor 502 signals the waveform generator 504to transmit 4406 an exploratory ultrasonic pulse to the end effector 125and then measures 4408 an ultrasonic property of the ultrasonic pulseupon transmission to the end effector 125.

Techniques for Delivering Pulsed RF and Ultrasonic Energy in aCombination Ultrasonic/RF Surgical Instrument

In one aspect, the present disclosure provides a technique fordelivering RF and ultrasonic energy to an end effector of a surgicalinstrument by controlling the power delivered to an end effector from agenerator, such as any one of the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), or a surgical instrument, such as the surgicalinstrument 108 (FIGS. 1-3). In accordance with the present technique,the power delivered to an end effector of a surgical instrument can bevaried based on properties or parameters of tissue interacting with theend effector. For conciseness and clarity of disclosure, the techniquesfor delivering RF and ultrasonic energy to the end effector will bedescribed with reference to the multifunction surgical instrument 108 ofFIG. 2 coupled to the generator 500 of FIG. 8, although it will beappreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

FIGS. 66-75 illustrate aspects of timing diagrams of energy pulses fordelivering different energy modalities to tissue. In one aspect thefirst energy modality is RF energy and the second energy modality isultrasonic energy. There are many benefits to a surgical device that iscapable of delivering both RF and ultrasonic energy. A surgicalinstrument capable of delivering both modalities provides stronger sealsand can cut tissue without the need of a separate knife. The followingdisclosure provides multiple pulsing techniques than can be utilized forvessel sealing. These techniques employ tissue impedance measurements,current measurements, can seal only, and can seal and cut tissue. Thesetechniques may be implemented using multiple generators, one generatorconfigured to deliver RF energy and another generator configured todeliver ultrasonic energy. Alternatively, these techniques may beimplemented with a single generator configured to deliver both RF andultrasonic energy. In other aspects, these techniques may be implementedwith a single generator that is configured to deliver RF and ultrasonicenergy simultaneously through a single output port.

These techniques comprise pulsing between RF and ultrasonic energymodalities to create strong seals. Multiple configurations of pulsingare disclosed. The pulse sequence timing diagrams illustrated in FIGS.57-63 and the logic flow diagrams shown in FIGS. 64-66 will be describedwith reference to the surgical instrument 108 of FIG. 2 coupled to thegenerator 500 of FIG. 8. Tissue is clamped between the clamp arm 145 andthe ultrasonic blade 149 of the end effector 125 of the surgicalinstrument 108 and then the generator 500 delivers the pulse sequencesdiscussed below.

FIG. 66 is a timing diagram of a seal only pulse sequence 4500illustrating a basic configuration of pulsing RF and ultrasonic energyfor “Seal Only” mode. The horizontal axis is time (t) in seconds thatthe energy is delivered or “pulsed.” The vertical axis is the currentpulse amplitude in milliamps (mA) that the pulse is capable of sourcing.The ultrasonic energy pulses 4502 are shown in dashed line and the RFpulses 4504 are shown in solid line. As shown in FIG. 66, the generator500 switches between the ultrasonic energy pulses 4502 and RF energypulses 4504 at fixed time intervals. During a first half cycle, thepulse sequence starts with the RF energy pulse 4504 ON for about 1 mS ata current pulse of about 750 mA amplitude while the ultrasonic energypulse 4502 is OFF for about 1 mS at 0 mA current amplitude. During thenext half cycle, the RF energy pulse 4504 is OFF for about 1 mS at 0 mAcurrent amplitude while ultrasonic energy pulse 4502 is ON for about 1ms at a current pulse of about 350 mA amplitude. The cycle is repeateduntil a strong tissue seal is developed. It will be appreciated that theapplication of the sequence of ultrasonic energy pulses 4502 and RFenergy pulses 4504 shown in the pulse sequence 4500 is suitable foreffecting a tissue seal only. This configuration of pulse sequence canstart either with an RF energy pulse 4504 or an ultrasonic energy pulse4502. Ultimately energy delivery for a “Seal Only” mode would be stoppedbased on the tissue impedance measured on the RF pulses 4504.

In order to reduce the risk of cutting tissue with the ultrasonic energypulses 4502, the number of ultrasonic energy pulses 4502 should beminimized. This configuration is shown in FIG. 67, which is a timingdiagram of a seal only pulse sequence 4510 illustrating a basicconfiguration of pulsing RF and ultrasonic energy for “Seal Only” mode.As shown, the pulse sequence 4500 starts with an active RF energy pulse4504. After two ultrasonic energy pulses 4502, or other predeterminedlimited number of ultrasonic energy pulses 4502, no more ultrasonicenergy pulses 4502 are delivered after the last ultrasonic energy pulse4502′ and the RF energy pulse 4504′ is delivered for an extended periodto effect a seal only. To avoid cutting the tissue with the ultrasonicenergy pulse 4504 the last RF energy pulse 4504′ remains ON at highamplitude while the ultrasonic energy pulse 4502 remains OFF.

It can be appreciated that the seal on the clamp arm 145 side may bewider and more complete than a seal on the ultrasonic blade 149 side.This may be caused by insufficient heating on the ultrasonic blade 149side due to the higher thermal mass of the ultrasonic blade 149. Inorder to address this issue, the ultrasonic energy pulse 4502 could beleft ON longer at the beginning to get the ultrasonic blade 149 up tothe sealing temperature. FIG. 68 is a timing diagram of a seal onlypulse sequence 4520 illustrating a basic configuration of pulsing RF andultrasonic energy to preheat the ultrasonic blade 149. FIG. 68 is atiming diagram of a seal only pulse sequence 4520. As shown in FIG. 68,the first energy pulse delivered is an ultrasonic energy pulse 4502,which is left ON for an extended period sufficient to preheat theultrasonic blade 149 prior to applying the RF energy pulses 4504. Toavoid cutting the tissue with the ultrasonic energy pulse 4504 the lastRF energy pulse 4504′ remains ON at high amplitude while the ultrasonicenergy pulse 4502 remains OFF.

FIG. 69 is a timing diagram of a seal only pulse sequence 4530. One ofthe main benefits to having more than one pulse of ultrasonic energy4502 is to maintain the ultrasonic blade 149 temperature. In order tomaintain ultrasonic blade 149 temperature and reduce the risk of cuttingtissue with the ultrasonic blade 149, the pulse sequence 4530 shown inFIG. 69 provides the first ultrasonic energy pulse 4502 at a highamplitude and then the subsequent ultrasonic energy pulses 4502′, 4502″at lower amplitudes. To avoid cutting the tissue with the ultrasonicenergy pulse 4504 the last RF energy pulse 4504′ remains ON at highamplitude while the ultrasonic energy pulse 4502 remains OFF.

The conditions for switching between the RF energy pulse 4504 and theultrasonic energy pulse 4502 could be based on a fixed time or it couldbe based on tissue impedance. For example, when a “Seal Only” mode isdesired, as shown in FIGS. 57-60, if a certain Impedance threshold isreached, the technique would not switch over to ultrasonic energy tominimize the risk of cutting through the tissue. The frequency slopecould also be used as a trigger to switch from ultrasonic energy pulse4502 delivery to RF energy pulse 4504 delivery.

If a “Seal and Cut” energy modality is desired, an ultrasonic energypulse 4502 step could be added to the end of any of the techniquesdescribed in connection with FIGS. 57-60. This could occur once acertain impedance threshold is met. FIGS. 61 and 62 illustrate timingdiagrams for seal and cut pulse sequences 4540, 4550 for issue seal andcut modes.

FIG. 70 is a timing diagram of a seal and cut pulse sequence 4540, whichbegins and ends with ultrasonic energy pulses 4502 delivered at the sameamplitude during the sealing a cutting cycles. A first ultrasonic energypulse 4502 is delivered at a predetermined amplitude and subsequentultrasonic energy pulses 4502 are delivered at the same predeterminedamplitude. The RF energy pulses 4504 are delivered until the tissue issealed or until the tissue impedance is equal to or greater than apredetermined threshold. After the last delivered RF energy pulse 4504′is turned OFF, the last ultrasonic energy pulse 4502′ is turned ON tocut tissue.

FIG. 71 is a timing diagram of a seal and cut pulse sequence 4550, whichbegins and ends with ultrasonic energy pulses 4502 delivered at variableamplitude during the sealing a cutting cycles. A first ultrasonic energypulse 4502 is delivered at a predetermined amplitude and subsequentultrasonic energy pulses 4502 are delivered at different amplitudes, andin one example as a stepped down amplitude. As shown, for example, asecond ultrasonic energy pulse 4502′ is delivered at an amplitude lowerthan the first amplitude and a third ultrasonic energy pulse 4502″ isdelivered at an amplitude that is lower the second predeterminedamplitude. The RF energy pulses 4504 are delivered until the tissue issealed or until the tissue impedance is equal to or greater than apredetermined threshold. After the last delivered RF energy pulse 4504′is turned OFF, the last ultrasonic energy pulse 4502′″ is turned ON tocut tissue. The last ultrasonic energy pulse 4502′″ may be delivered atan amplitude that either the same as the first amplitude, may bedifferent than previous amplitudes, or may be equal to one of theintermittent amplitudes.

For the seal and cut pulse sequences 4540, 4550, on thick tissueapplications, the ultrasonic modality take approximately 250 ms to seek,meaning that low pulse widths result in a short amount of therapeutictime. In some aspects, pulse widths longer than 500 ms, for example, mayprovide certain benefits.

FIG. 72 is a timing diagram of a seal only pulse sequence 4560 where theultrasonic energy pulse 4502 current is be set based on the impedancemeasured with the preceding RF energy pulse 4504. The right verticalaxis is tissue impedance in Ohms. The ultrasonic energy pulse 4502current could be set based on the impedance measured with the precedingRF energy pulse 4504. It would be preferred to have the ultrasonicenergy pulse 4502 current high when the preceding RF impedance was low.As the RF impedance increases the ultrasonic energy pulse 4502 currentof the next pulse would decrease. This would allow the technique tocompensate for the amount of tissue positioned within the jaws of theend effector 125, where thick tissue/bundle applications would stay atlower impedance for a longer period of time and would require moreenergy/heat to seal. As shown in FIG. 72, based on the first two lowtissue impedance 4506 measurements the ultrasonic energy pulse 4502current amplitude remains the same. After the third tissue impedance4506′ measurement, the amplitude of the ultrasonic energy pulse 4502′current is reduced until the tissue impedance exceeds a predeterminedthreshold and the RF energy pulse 4504′ current remains ON while theultrasonic energy pulse 4502 current amplitude remains at 0mA.

In one aspect the first energy modality is RF energy and the secondenergy modality is ultrasonic energy. In one aspect, the processdepicted by the logic flow diagram 4600 may be repeated until the tissueis sealed. As discussed in connection with FIGS. 57-60, in a seal onlymethod, the ultrasonic energy modality may be turned off after a fewpredetermined number of cycles or based on tissue impedance measurementsto avoid cutting the tissue while the RF energy modality is delivered tomake a tissue seal. The ultrasonic and/or the RF energy modalities maybe delivered at the same amplitude or at variable amplitudes. Forexample, the RF energy modality may be delivered at the same amplitudewhereas the amplitude of the ultrasonic energy modality is stepped down.As discussed in connection with FIGS. 61 and 62, during a seal and cutcycle, the ultrasonic energy modality is delivered last to effect atissue after the tissue is sealed. As previously discussed, during thesealing cycle, the amplitude of the ultrasonic energy modality may bethe same or may be stepped down. A discussed in connection with FIG. 72,in a seal only method, the amplitude of the ultrasonic energy modalityis adjusted base don the previous tissue impedance measurement utilizingthe RF energy modality. In any of the seal or seal and cut methodsdiscussed above, the ultrasonic energy may be delivered first to preheathe ultrasonic blade 149 because of the higher thermal mass of theultrasonic blade 149 with respect to the thermal mass of the clamp arm145.

FIG. 73 is a logic flow diagram 4600 of a technique for deliveringpulses of different energy modalities to tissue. As described herein,the logic flow diagram 4600 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 4600 of FIG. 73, initially,tissue is clamped between the clamp arm 145 and the ultrasonic blade 149of the end effector 125 of the surgical instrument 108 and then theprocessor 502 signals the waveform generator 504 to deliver the pulsesequences discussed below. In accordance with the method, the processor502 activates 4602 a first energy modality of the surgical instrument108. After a first period, the processor 502 deactivates 4604 the firstenergy modality and activates 4606 a second energy modality for a secondperiod. The second energy modality is activated 4606 independent of thefirst energy modality. After the second period expires, the processor502 deactivates 4608 the second energy modality.

FIG. 74 is a logic flow diagram 4700 of a technique for deliveringpulses of different energy modalities to tissue. As described herein,the logic flow diagram 4700 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 4700 of FIG. 74, initially,tissue is clamped between the clamp arm 145 and the ultrasonic blade 149of the end effector 125 of the surgical instrument 108 and then theprocessor 502 signals the waveform generator 504 to deliver the pulsesequences discussed herein. In accordance with the method, the processor502 activates 4702 an RF energy modality of the surgical instrument 108to drive RF energy through electrodes located in the clamp arm 145 ofthe end effector 125. The processor 502 deactivates 4704 the RF energymodality upon detecting a first predetermined tissue impedance Z_(T1)measured at the end effector 125 of the surgical instrument 108. Thegenerator 500 then activates 4706 an ultrasonic energy modality of thesurgical instrument 108 to drive the ultrasonic blade 149. The processor502 deactivates 4708 the ultrasonic energy modality upon detecting asecond predetermined tissue impedance Z_(T2) at the end effector 125 ofthe surgical instrument 108. As previously discussed, the tissueimpedance is determined by the processor 502 by dividing the voltageapplied to the end effector 125 by the current delivered to the endeffector 125. For example, the processor 502 can determine the tissueimpedance by dividing the voltage sensed by the second voltage sensingcircuit 524 by the current sensed by the current sensing circuit 514.

FIG. 75 is a logic flow diagram 4000 of a technique for deliveringpulses of different energy modalities to tissue. As described herein,the logic flow diagram 4800 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 4800 of FIG. 75, initially,tissue is clamped between the clamp arm 145 and the ultrasonic blade 149of the end effector 125 of the surgical instrument 108 and then theprocessor 502 signals the waveform generator 504 to deliver the pulsesequences discussed herein. In accordance with the method, the processor502 activates 4802 an RF energy modality of the surgical instrument 108to drive RF energy through electrodes located in the clamp arm 145 ofthe end effector 125. The processor 502 deactivates 4804 the RF energymodality upon the expiration of a first predetermined period T₁. Theprocessor 502 activates 4806 an ultrasonic energy modality of thesurgical instrument 108 to drive the ultrasonic blade 149. The processor502 deactivates 4808 the ultrasonic energy modality upon the expirationof a second predetermined period T₂.

Techniques for Simultaneously Delivering Blasts of Ultrasonic and RFEnergy in a Combination Ultrasonic/RF Surgical Instrument

In one aspect, the present disclosure provides a technique fordelivering a combination simultaneous blast of RF and ultrasonic energyto an end effector of a surgical instrument by controlling the powerdelivered to an end effector from a generator, such as any one of thegenerators 102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8), or a surgicalinstrument, such as the surgical instrument 108 (FIGS. 1-3). Inaccordance with the present technique, a combination simultaneous blastof RF and ultrasonic energy can be delivered to an end effector of asurgical instrument can be varied based on properties or parameters oftissue interacting with the end effector. For conciseness and clarity ofdisclosure, the techniques for delivering a combination simultaneousblast of RF and ultrasonic energy to the end effector will be describedwith reference to the multifunction surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

FIGS. 76-80 illustrate aspects of delivering multiple energy modalitiesto tissue. In one aspect the first energy modality is RF energy and thesecond energy modality is ultrasonic energy. There are many benefits toa surgical device that is capable of delivering both RF and ultrasonicenergy. A surgical instrument capable of delivering both modalitiesprovides stronger seals and can cut tissue without the need of aseparate knife. The following disclosure provides multiple pulsingtechniques than can be utilized for vessel sealing. These techniquesemploy tissue impedance measurements, current measurements, can sealonly, and can seal and cut tissue.

The various aspects described below provides simultaneous activation ofmultiple energy modalities such as RF and ultrasonic energy modalities.Initially both RF and ultrasonic modalities are delivered to tissue. TheRF energy modality is utilized for the first portion of the seal. Aftera set amount of time T₁, based off the RF impedance Z_(T) detected, theultrasonic modality is terminated. A short blast of ultrasonic energy atthe beginning of the seal cycle provides benefits to sealing, as it aidsin heating the ultrasonic blade and subsequently the tissue surface incontact with the blade while the electrode is simultaneously heating thetissue surface in contact with the RF electrodes.

These techniques may be implemented using multiple generators, onegenerator configured to deliver RF energy and another generatorconfigured to deliver ultrasonic energy. Alternatively, these techniquesmay be implemented with a single generator configured to deliver both RFand ultrasonic energy. In other aspects, these techniques may beimplemented with a single generator that is configured to deliver RF andultrasonic energy simultaneously through a single output port. Thesetechniques comprise simultaneous pulsing of RF and ultrasonic energymodalities to create strong seals. Multiple configurations of pulsingare disclosed. Multiple configurations of the simultaneous techniquesare disclosed.

FIG. 76 is a logic flow diagram 4900 of one aspect of a process ofapplying simultaneous activation of different energy modalities totissue. As described herein, the logic flow diagram 4900 may beimplemented in the generator 500, the multifunction surgical instrument108, or a combination thereof. With reference now to the logic flowdiagram 4900 of FIG. 76, tissue is clamped between the clamp arm 145 andthe ultrasonic blade 149 of the end effector 125 of the surgicalinstrument 108 and then the generator 500 delivers the simultaneousenergy modalities. The total seal time 4902 is shown along a verticalaxis.

Once tissue is clamped between the clamp arm 145 and the ultrasonicblade 149 of the end effector 125 of the surgical instrument 108, theprocessor 502 signals the waveform generator 504 to deliver the pulsesequences discussed herein. In accordance with the logic flow diagram4900 of FIG. 76, the RF energy modality application process 4904 isshown on the left and ultrasonic energy modality application process4916 is shown on the right. The processor 502 activates 4996 the RFenergy modality at the same time that the ultrasonic energy modality isactivated 4918. Once the RF energy modality is activated 4906, theprocessor 502 signals the waveform generator 504 to deliver 4908 RFenergy in accordance with a variety of RF sealing techniques, includingRF sealing techniques described herein in connection with the logicdiagram 5400 shown FIG. 81. Turning back to FIG. 76, the processor 502activates 4920 the ultrasonic energy modality at a constant power level.During the simultaneous application of the RF and ultrasonic energymodalities, the processor 502 measures the RF tissue impedanceZ_(tissue) and when the RF tissue impedance Z_(tissue) meets ore exceedsan ultrasonic termination impedance Z_(US-term) (see FIG. 77) it isprovided 4910 as feedback to the processor 502 to signal 4922 thewaveform generator 504 and amplifier 506 to terminate 4924 delivery ofultrasonic energy to the end effector 125. Meantime, the RF energymodality is continuously delivered until an RF termination impedanceZ_(RF-term) is reached 4912 at which point the processor 502 signals thewaveform generator 504 to terminate 4914 delivery of RF energy. Theshort blast of the ultrasonic energy at the beginning of the seal cycleprovides benefits to sealing, as it aids in heating the ultrasonic blade149 and subsequently the tissue surface in contact with the blade 149while the electrode in the clamp arm 145 is simultaneously heating thetissue surface in contact with the electrode. As previously discussed,the tissue impedance is determined by the processor 502 by dividing thevoltage applied to the end effector 125 by the current delivered to theend effector 125. For example, the processor 502 can determine thetissue impedance by dividing the voltage sensed by the second voltagesensing circuit 524 by the current sensed by the current sensing circuit514.

FIG. 77 is a graphical representation of RF Impedance versus Time inconnection with the logic flow diagram 4900 of FIG. 76 to illustrate theultrasonic termination impedance. The horizontal axis is time (ms) andthe vertical axis is RF impedance (Ohms). The tissue impedanceZ_(tissue) curve 5002 is monitored during the sealing period utilizingthe RF energy. When the tissue impedance Z_(tissue) reaches theultrasonic termination impedance Z_(US-term) 5004 the ultrasonic poweris terminated and when the tissue impedance Z_(tissue) reaches the RFtermination impedance Z_(RF-term) 5006 the RF energy is terminated.

FIG. 78 illustrates an example of the quality of a seal 5102 made in avessel 5100 using the simultaneous activation of RF and ultrasonicenergy modalities as described in connection with FIGS. 67 and 68. Themain advantage of simultaneous activation of RF and ultrasonic energymodalities is that the ultrasonic energy heats up the ultrasonic blade149 and helps to create a reduction in the difference in thermal massbetween the ultrasonic blade 149 and the electrode in the clamp arm 145.During a non-simultaneous activation seal cycle utilizing both RF andultrasonic modalities, a challenge is posed to create a strong seal withvarying thermal masses on either side of the end effector 125 jaw.

FIG. 79 is a graphical representation 5200 of seal burst pressure ofcarotid bundles versus an RF only seal and a simultaneous RF/ultrasonicseal as described in connection with FIGS. 67-69. The horizontal axis isan RF seal only boxplot 5202 and a simultaneous RF/ultrasonic boxplot5204. The boxplots 5202, 5204 demonstrate the tissue effect advantagesdescribed ion connection with the simultaneous RF/ultrasonic energymodality activation process 4100 shown in connection with FIG. 76 wheresimultaneously heating the ultrasonic blade and electrode provides ahigh quality 5102 in a vessel as shown in FIG. 78.

FIG. 80 is a logic flow diagram 5300 of a process of simultaneousactivation of RF and ultrasonic energy modalities. As described herein,the logic flow diagram 5300 may be implemented in the generator 500, themultifunction surgical instrument 108, or a combination thereof. Withreference now to the logic flow diagram 5300 of FIG. 80, initially,tissue is clamped between the clamp arm 145 and the ultrasonic blade 149of the end effector 125 of the surgical instrument 108 and then theprocessor 502 signals the waveform generator 504 to deliver the pulsesequences discussed herein. In accordance with the logic flow diagram5300, the processor 502 simultaneously activates 5302 an RF energymodality and an ultrasonic energy modality of the surgical instrument108. The processor 502 monitors 5304 the tissue impedance using RFenergy modality. When the tissue impedance is equal to or greater than afirst termination impedance, the generator 500 deactivates 5306 theultrasonic energy modality of the surgical instrument 108. The RF energymodality is delivered until the tissue impedance is equal to or greaterthan a second termination impedance, at which time the processor 502deactivates 5308 the RF energy modality of the surgical instrument 108and the tissue seal is complete.

In some aspects utilizing a pulsed drive signal, a generator, such as,for example, one of generators 102, 200, 300, 400, 500 described inconnection with FIGS. 1-3 and 5-8, may apply one or more composite loadcurves to the drive signal, and ultimately to the tissue. Composite loadcurves may define a level of power to be delivered to the tissue as afunction of a measured tissue property or properties (e.g., impedance).Composite load curves may, additionally, define pulse characteristics,such as pulse width, in terms of the measured tissue properties.

FIG. 81 illustrates one aspect of a logic diagram 5400 for the selectionand application of composite load curves by any one of generators 102,200, 300, 400, 500. It will be appreciated that the logic diagram 5400may be implemented with any suitable type of generator or surgicaldevice. According to various aspects, the logic diagram 5400 may beimplemented utilizing an electrosurgical instrument, such as theelectrosurgical instrument 106 described above with respect to FIG. 1,an ultrasonic surgical instrument 104 described above with respect toFIG. 1, or a combination surgical instrument 108 described above withrespect to FIGS. 1-3.

Referring back to FIG. 81, a control process 5402 may be executed, forexample by a digital device of the generator 102 to select and applycomposite load curves 5406, 5408, 5410, 5412. The control process 5402may receive a time input from a clock 5404 and may also receive loopinput 5424 from sensors 5418. The loop input 5424 may representproperties or characteristics of the tissue that may be utilized in thecontrol process 5402 to select and/or apply a composite load curve.Examples of such characteristics may comprise, for example, current,voltage, temperature, reflectivity, force delivered to the tissue,resonant frequency, rate of change of resonant frequency, etc. Thesensors 5418 may be dedicated sensors (e.g., thermometers, pressuresensors, etc.) or may be software implemented sensors for derivingtissue characteristics based on other system values (e.g., for observingand/or calculating voltage, current, tissue temperature, etc., based onthe drive signal). The control process 5402 may select one of thecomposite load curves 5406, 5408, 5410, 5412 to apply, for example basedon the loop input 5424 and/or the time input from the clock 5404.Although four composite load curves are shown, it will be appreciatedthat any suitable number of composite load curves may be used.

The control process 5402 may apply a selected composite load curve inany suitable manner. For example, the control process 5402 may use theselected composite load curve to calculate a power level and one or morepulse characteristics based on tissue impedance (e.g., currentlymeasured tissue impedance may be a part of, or may be derived from, theloop input) or resonant frequency characteristics of a ultrasonicsurgical instrument 104. Examples of pulse characteristics that may bedetermined based on tissue impedance according to a composite load curvemay include pulse width, ramp time, and off time.

At set point 5414, the derived power and pulse characteristics may bedelivered to the drive signal. In various aspects, a feedback loop 5422may be implemented to allow for more accurate modulation of the drivesignal. At the output of the set point 5414, the drive signal may beprovided to an amplifier 5416, which may provide suitable amplification.The amplified drive signal may be provided to a load 5420 (e.g., viasensors 5418). The load 5420 may comprise the tissue, the surgicalinstrument 104, 106, 108, and/or any cable electrically coupling agenerator with the surgical instrument 104, 106, 108 (e.g., cables 142,144, 146).

In various aspects the state of coagulation may be determined usingneural networks that are configured to take a plurality of factors intoaccount. In some aspects, a generator may be configured to drive bothultrasonic and electrosurgical systems and include a nested neuralnetwork to identify whether the generator is presented with a true shortcircuit vs. a low impedance tissue. In addition, in some aspects, toassist in the detection of short circuits, the neural network may beconfigured to track and store at least the following factors: a.Measured resistance/impedance; b. Drive current (RMS); c. Drive Voltage(RMS); and d. Moving average of measured impedance. In some aspects, theneural network will be thought to in order to be capable of discerningbetween a true short and low impedance tissue. In other aspects, aneural network may be programmed to identify properties in metal,tissues, and other non-tissue elements. The neural network also may beconfigured to transmit the exploratory pulse to the transducer. Inaddition, new developments or additional programs, including receivingfeedback from the attempts to detect short circuits, may be incorporatedback into the neural network to increase its situational awareness andeffectively better learn how to detect a true short circuit. Withconfirmation of a short circuit both by RF and ultrasonic functionality,this can allow for less time spent getting repeat errors on RF andfaster transection on low impedance tissue. An example of a neuralnetwork is described in connection with FIG. 82.

FIG. 82 illustrates one aspect of a neural network 5500 for controllinga generator. FIG. 73 illustrates one aspect of an artificial neuralnetwork 5500 for generating an estimated temperature T_(est) resultingfrom an application of ultrasonic energy using an ultrasonic surgicalinstrument, such as the ultrasonic surgical instruments 104, 106, 108(FIGS. 1-3). In certain aspects, the neural network 5500 may beimplemented in the processor and/or the programmable logic device of thegenerator 102 (FIG. 1). The neural network 5500 may comprise an inputlayer 5502, one or more nodes 5504 defining a hidden layer 5506, and oneor more nodes 5508 defining an output layer 5510. For the sake ofclarity, only one hidden layer 5506 s shown. In certain aspects, theneural network 5500 may comprise one or more additional hidden layers ina cascaded arrangement, with each additional hidden layer having anumber of nodes 5504 that may be equal to or different from the numberof nodes 5504 in the hidden layer 5506.

Each node 5504, 5508 in the layers 5502, 5510 may include one or moreweight values w 5512, a bias value b 5514, and a transform function ƒ5516. In FIG. 82, the use of different subscripts for these values andfunctions is intended to illustrate that each of these values andfunctions may be different from the other values and functions. Theinput layer 5502 comprises one or more input variables p 5518, with eachnode 5504 of the hidden layer 5506 receiving as input at least one ofthe input variables p 5518. As shown in FIG. 82, for example, each node5504 may receive all of the input variables p 5518. In other aspects,less than all of the input variables p 5518 may be received by a node5504. Each input variable p 5518 received by a particular node 5504 isweighted by a corresponding weight value w 5512, then added to any othersimilarly weighted input variables p 5518, and to the bias value b 5512.The transform function ƒ 5516 of the node 5504 is then applied to theresulting sum to generate the node's output. In FIG. 82, for example,the output of node 5504-1 may be given as f₁(n₁), wheren₁=(w_(1,1)·p₁+w_(1,2)·p₂+ . . . +W_(1,j)·p_(j))+b₁.

A particular node 5508 of the output layer 5510 may receive an outputfrom one or more of the nodes 5504 of the hidden layer 5506 (e.g., eachnode 5508 receives outputs f₁(·),f₂(·), . . . , f_(j)(·) from respectivenodes 5504-1, 5504-2, . . . , 5504-i in FIG. 82), with each receivedoutput being weighted by a corresponding weight value w 5512 andsubsequently added to any other similarly weighted received outputs, andto a bias value b 5514. The transform function ƒ 5516 of the node 5508is then applied to the resulting sum to generate the node's output,which corresponds to an output of the neural network 5500 (e.g., theestimated temperature T_(est) in the aspect of FIG. 82). Although theaspect of the neural network 5500 in FIG. 82 comprises only one node5508 in the output layer 5510, in other aspects the neural network 5500may comprise more than one output, in which case the output layer 5510may comprise multiple nodes 5508.

In certain aspects, the transform function ƒ 5516 of a node 5504, 5508may be a nonlinear transfer function. In one aspect, for example, one ormore of the transform functions ƒ 5516 may be a sigmoid function. Inother aspects, the transform functions ƒ 5516 may include a tangentsigmoid, a hyperbolic tangent sigmoid, a logarithmic sigmoid, a lineartransfer function, a saturated linear transfer function, a radial basistransfer function, or some other type of transfer function. Thetransform function ƒ 5516 of a particular node 5504, 5508 may be thesame as, or different from, a transform function ƒ 5516 in another node5504, 5508.

In certain aspects, the input variables p 5518 received by the nodes5504 of the hidden layer 5506 may represent, for example, signals and/orother quantities or conditions known or believed to have an effect onthe temperature or heating resulting from an application of ultrasonicenergy. Such variables may comprise, for example, one or more of: drivevoltage output by the generator 102, drive current output by thegenerator 102, drive frequency of the generator output 102, drive poweroutput by the generator 102, drive energy output by the generator 102,impedance of the ultrasonic transducer 120, and time duration over whichultrasonic energy is delivered. Additionally, one or more of the inputvariables p 5518 may be unrelated to outputs of the generator 102 andmay comprise, for example, characteristics of the end effector 122, 125(e.g., blade tip size, geometry, and/or material) and a particular typeof tissue targeted by the ultrasonic energy.

The neural network 5500 may be trained (e.g., by changing or varying theweight values w 5512, the bias values b 5514, and the transformfunctions ƒ 5516) such that its output (e.g., estimated temperatureT_(est) in the aspect of FIG. 82) suitably approximates a measureddependency of the output for known values of the input variables p 5518.Training may be performed, for example, by supplying known sets of inputvariables p 5518, comparing output of the neural network 5500 tomeasured outputs corresponding to the known sets of input variables p5518, and modifying the weight values w 5512, the bias values b 5514,and/or the transform functions ƒ 5516 until the error between theoutputs of the neural network 5500 and the corresponding measuredoutputs is below a predetermined error level. For example, the neuralnetwork 5500 may be trained until the mean square error is below apredetermined error threshold. In certain aspects, aspects of thetraining process may be implemented by the neural network 5500 (e.g., bypropagating errors back through the network 5500 to adaptively adjustthe weight values w 5512 and/or the bias values b 5514).

FIG. 83 illustrates an example graph of a curve 5600 of impedance (|Z|)versus time (t) showing the termination impedance at which a propertissue seal is achieved using RF energy. The curve 5600 provides time inseconds along the horizontal axis and impedance in Ohms along thevertical axis. The impedance versus time curve 5600 is described inthree sections 5602, 5604, and 5606. Section one 5602 represents theinitial impedance of the tissue from a time 5608 just after energy isapplied to the tissue to a time 5610 when the tissue impedance drops toa minimum value as shown in section two 5604. Section one 5602 of thecurve 5600 decreases for an initial impedance |Z| value until itstabilizes to a minimum impedance in the second section 5604 of thecurve 5600. After energy is delivered to the end effector and applied tothe tissue for a certain period (e.g., 4.5 seconds as shown) themoisture content of the tissue evaporates causing the tissue to dry outand the impedance of the tissue to rise in section three 5606 of thecurve until the termination impedance |Z_(T)| is reached, at which pointin time, T_(o), the energy to the end effector is shut off. The portionof the curve 5600 in section three 5606 (shown in dashed line)represents the increase in tissue impedance |Z| that would result if theenergy were be applied continuously instead of being shut off at thetermination impedance |Z_(T)| point.

Once the termination impedance |Z_(T)| has been reached, the generatormay switch from delivering RF energy to ultrasonic energy. Thetermination impedance |Z_(T)| can be a fixed value based on theinstrument's electrode and compression properties or it can be avariable that depends on factors measured during the grasping andcoagulation cycle such as: amount of tissue grasped, initial impedanceand minimum impedance. It also can be a variable dependent on variousslopes of impedance, energy delivery at various points in thecoagulation cycle such as minimum impedance, and/or inflection points,and combinations thereof.

Tissue impedance as a function of time is a continuous differentiablefunction of time. It can be shown, through system identificationtechniques and system parameter optimization that a model exists whichcan model the relationship of the power input to tissue. The form of themodel is:

$\begin{matrix}{\overset{¨}{Z} = \left\{ \begin{matrix}{{{kZ} + {b_{1}\overset{.}{Z}} + {{c_{1}\left( {W - c_{2}} \right)}\mspace{14mu}{if}\mspace{14mu}\overset{.}{Z}}} < 0} \\{{{kZ} + {b_{2}\overset{.}{Z}} + {{c_{1}\left( {W - c_{2}} \right)}\mspace{14mu}{if}\mspace{14mu}\overset{.}{Z}}} \geq 0}\end{matrix} \right.} & {{Equation}\mspace{14mu} 3}\end{matrix}$

In Equation 3, Z is the impedance measured (estimated from known currentand voltage) across the tissue, Ż and {umlaut over (Z)} are the firstand second derivatives of the tissue impedance. k, b₁, b₂ c₁, and c₂ arethe parameters to be estimated. W is the work applied to the tissue inJoules. Using a combination of downhill simplex and global basedoptimization techniques, such as, for example evolutionary processes,particle swarm optimization, and simulated annealing. The parameters canbe estimated in quasi-real time, which are below user noticeable timeperiods.

FIG. 84 displays curves 5702, 5704 of tissue impedance versus time oftissue impedance with 40 W of RF power delivered to tissue using adownhill simplex technique for a model of tissue 5702 and experimentaldata 5704. As shown in FIG. 84, the curves 5702, 5704 are similar to thecurve 2500 shown in FIG. 83.

As demonstrated by the curves of FIG. 84, constant power may be appliedto tissue while in the time period 0 seconds to approximately 8.8seconds, the curves 5702, 5704 have a distinct shape that may bereferred to as a “bathtub,” due to the characteristic bathtub shape ofthe tissue impedance as a function of time while power is applied to thetissue during the sealing process. Once system identification hasoccurred during the tissue “bathtub” period to estimate k, b₁, b₂, c₁,and c₂ of Equation 1 above, a post “bathtub” impedance control techniquecan be configured for tissue interacting with the end effector 125 ofthe surgical instrument 108.

One post “bathtub” impedance control technique utilizes parameterestimation to determine tissue characteristics. In one aspect, theparameters estimated during the “bathtub” phase may relate to certaintissue properties, such as, for example tissue type, tissue amount, andtissue state. A predetermined controller can be selected from a range ofcontrollers that best match the parameters estimated based on a lookuptable

Another post “bathtub” impedance control technique utilizes a linearquadratic controller (LQR) with precompensation. A linear quadraticcontroller is a well-known and used controller which can be designed inreal time and will result in optimal control of tissue impedance and therate of change of impedance. In one aspect, an LQR controller can beimplemented in the following form:

$\begin{matrix}{W = {{{Nb}*r} - {K\begin{bmatrix}Z \\\overset{.}{Z}\end{bmatrix}} + c_{2}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

It is assumed that K is the control gain and r is a desired referenceset point and Nb is a precompensation gain to prevent steady stateerror. From this system, rate rise can be controlled explicitly. Thesecond order differential equation shown in Equation 4 is to be reducedto two first order equations for each value of b₁ and b₂. However, if itis assumed that the goal of post “bathtub” energy application willresult in Ż>0 ∀ t>0 (that is, Ż>0 for all time values after the start ofenergy application when t=0) then it can be assumed that the controllermust be designed for b=b₂. The reduction to first order is shown inEquation 5:Let Z=U ₁ and Ż=U ₂then through substitution:

$\begin{matrix}{\begin{bmatrix}{\overset{.}{U}}_{1} \\{\overset{.}{U}}_{2}\end{bmatrix} = {{\begin{bmatrix}0 & 1 \\k & b\end{bmatrix}\begin{bmatrix}U_{1} \\U_{2}\end{bmatrix}} + {\begin{bmatrix}0 \\1\end{bmatrix}\left( {W - c_{2}} \right)}}} & {{Equation}\mspace{14mu} 5}\end{matrix}$

For such a system, the optimal control input K can be found by reducinga cost function of a particular form and solving the Ricatti algebraicequation. The control cost function to be reduced has the form given inEquation 4 and is common to all LQR controllers.

$\begin{matrix}{J = {\int_{0}^{\infty}{\left( {{\begin{bmatrix}U_{1} & U_{2}\end{bmatrix}{Q\ \begin{bmatrix}U_{1} \\U_{2}\end{bmatrix}}} + {\begin{bmatrix}0 & W\end{bmatrix}{R\begin{bmatrix}0 \\W\end{bmatrix}}} + {{2\begin{bmatrix}U_{1} & U_{2}\end{bmatrix}}{N\begin{bmatrix}0 \\W\end{bmatrix}}}} \right)d\; t}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

R, N, and Q are predetermined constant matrices related to the costfunction being reduced and controller performance. They are selected bythe design engineer to regulate the controller's performance. When thisprocess is completed, K is given by:K=R ⁻¹(B ^(T) P(t)+N ^(T)  Equation 7

In Equation 5, P is the solution to the algebraic Riccati equation inEquation 8:A ^(T) P+PA−(PB+N)R ⁻¹(B ^(T) P+N ^(T))+Q=0  Equation 8

According to one aspect, upon fitting a model to experimental datapoints, such as that show in FIG. 84 for curves 5702 and 5704respectively, Equation 5 may be used to create an optimal controllerthat holds impedance at a steady state value, r=250 Ohm. FIG. 85displays curves 5802 and 5804 that represent the modeled data and theexperimental data, respectively. As shown in FIG. 85, the controllerperformed as expected on a fitted tissue model where the desiredimpedance 5806, Z, is held at 250 Ohm. For the controller shown in FIG.85, K=[1.9237 4.3321] and Nb=[26.9532]. A range of appropriate gainsexist and can be determined. Similarly, a range of feasible gains forthe model development can also be determined.

Additionally, a controller also may be configured to operate as atracking controller to manipulate Ż by updating the reference rappropriately in time. An example of such a controller is illustrated inFIG. 86, where curves 5902 and 5904 that represent the modeled data andthe experimental data, respectively, and line 5906 is the desiredimpedance for one aspect of a tracking controller. As shown in FIG. 86,a desired tissue impedance, where the desired impedance is based on arate of change of the tissue impedance, may be achieved. Steady stateperformance with a tracking controller can be improved by incorporatingan integrator to the system of equations shown by Equation 7.

FIG. 87 is a logic flow diagram 6000 of a method for identifying atissue type and developing a control process to control the applicationof an energy modality to the tissue according to tissue impedance. Asdescribed herein, the logic flow diagram 6000 may be implemented in thegenerator 500, the multifunction surgical instrument 108, or acombination thereof. With reference now to the logic flow diagram 6000shown in FIG. 87, tissue is clamped between the clamp arm 145 and theultrasonic blade 149 of the end effector 125 of the surgical instrument108. In accordance with the method, the generator 500 may not be able todetermine a tissue type located between the clamp arm 145 and theultrasonic blade 149 of the end effector 125. In accordance with themethod, the processor 502 signals the waveform generator 504 to deliver6002 an energy modality to the end effector 125 of the surgicalinstrument 108.

The processor 502 measures 6004 tissue impedance. Application of theenergy modality ceases 6006 upon the processor 502 determining that thetissue impedance matches a predetermined threshold tissue impedance. Theprocessor 502 estimates 6008 at least one tissue parameter based atleast partially on the measured tissue impedance. According to variousaspects, the at least one tissue parameter comprises a tissue type, atissue amount, a tissue state, or a combination thereof. The processor502 develops 6010 a parameterized tissue model based on the at least oneestimated tissue parameter and generates 6012 a control technique forapplication of the energy modality based on the parameterized tissuemodel. Accordingly, the energy modality may be applied to another tissueportion according to the control process.

In another aspect, generating the control process may comprisecorrelating specific tissue characteristics with the application of theenergy modality to the tissue. Furthermore, the control process may begenerated in real time such that it readily available for use on furtherapplications to tissue. In addition, the control process may beconfigured to apply the energy modality so the tissue impedance matchesa predetermined threshold value or a predetermined rate of change.

Ultrasonic Output Controlled by RF Impedance Trajectory

In one aspect, the present disclosure provides ultrasonic outputcontrolled by RF impedance trajectory to control the power output from agenerator, such as any one of the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), or the surgical instrument 108 (FIGS. 1-3). Thepower delivered to an end effector of a surgical instrument can varybased on the tissue RF impedance trajectory. For conciseness and clarityof disclosure, the techniques for ultrasonic output controlled by RFimpedance trajectory to control the power output from a generator willbe described with reference to the surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

According to one aspect, a surgical instrument may uses an RF energymodality to sense tissue characteristics, such as impedance, and thechanges of the tissue characteristics to modulate the output power of anultrasonic tissue treating system. Specifically, the output power of asurgical instrument may be modulated as a function of a desiredimpedance trajectory where the impedance trajectory results in a desiredtissue effect or outcome. The RF output may be therapeutic, e.g. tissuetreating, or sub-therapeutic, e.g. sensing only. Further, the RF outputmay be applied to the tissue and the voltage and current, orrepresentations of the voltage and current, are measured or estimated.In addition, the impedance may be calculated by determining the ratio ofthe voltage to the current.

FIG. 88 is a logic flow diagram 6100 of a method for treating tissue. Asdescribed herein, the logic flow diagram 6100 may be implemented in thegenerator 500, the multifunction surgical instrument 108, or acombination thereof. With reference now to the logic flow diagram 6100shown in FIG. 88, tissue is clamped between the clamp arm 145 and theultrasonic blade 149 of the end effector 125 of the surgical instrument108. In accordance with the method, the processor 502 signals thewaveform generator 504 to deliver 6102 an energy modality to the endeffector 125 of the surgical instrument 108. According to variousaspects, the energy modality may be an RF energy modality or anultrasonic energy modality, or a blended combination thereof, and theamplitude may be a therapeutic amplitude, a sub-therapeutic amplitude,or a combination thereof. The processor 502 measures 6104 tissueimpedance and signals the waveform generator 504 to modulate 6106 thedelivery of the selected energy modality based on the measured tissueimpedance. Ultimately, the processor 502 signals the waveform generator504 to cease 6108 the application of the energy modality upon meeting orexceeding a termination impedance threshold that corresponds to a tissueparameter, such as, for example, that the seal is complete. Theapplication of the energy modality may cease upon the tissue impedancematching a predetermined threshold value of tissue impedance or apredetermined threshold rate of change of tissue impedance. Theimpedance may be determined by the processor 502 by dividing the outputof the second voltage sensing circuit 524 is coupled across theterminals labeled ENERGY2/RETURN by the output of the current sensingcircuit 514 is disposed in series with the RETURN leg of the secondaryside of the power transformer 508 as shown in FIG. 8.

In accordance with the logic flow diagram 6100, the surgical instrument108 may further determine that the tissue is sealed based on measuringat least one of an initial tissue impedance, an initial jaws-aperture ofan end effector, a current tissue impedance, a rate of change of tissueimpedance, an amount of energy driven into the tissue, a transactiontime for the energy modality and/or determining a state of the tissuebased on the measured tissue impedance of the tissue. The state of thetissue may comprise one of coagulated, sealed, or cut, for example.

Modulating application of the energy modality based on the measuredtissue impedance may comprise applying the energy modality to cause thetissue impedance to change according to a predetermined course. Invarious aspects, the predetermined course comprises a predeterminedthreshold value of tissue impedance of the tissue or a predeterminedthreshold rate of change of tissue impedance of the tissue. In anotheraspect, modulating application of the energy modality based on themeasured tissue impedance comprises modifying an output power of agenerator, modifying an output waveform of the generator, selectinganother energy modality to apply to the tissue, modifying thetermination parameter. Additionally, the energy modality may be a firstenergy modality and the method further comprises applying a secondenergy modality to tissue at a second amplitude. The first energymodality may be an RF energy modality and the second energy modality maybe an ultrasonic energy modality

In another aspect, the generator 500 may comprise an ultrasonic output(ENERGY1/RETURN) configured to deliver a drive signal to an ultrasonictransducer 120 coupled to an ultrasonic blade 149 of the surgicalinstrument 108. The generator 500 also may comprise an RF output(ENERGY2/RETURN) configured to deliver an electrosurgical RF drivesignal to at least one electrode located in the arm 145 of the surgicalinstrument 108. The generator 500 also may comprise sensing circuitrysuch as a second voltage sensing circuit 524 and a current sensingcircuit 514 configured to measure tissue impedance, and a processor 502configured to determine whether a tissue reaction has occurred based ona measured tissue impedance of the tissue and a predetermined change inthe measured tissue impedance. The waveform generator 504 and amplifier506 are controlled by the processor 502 to provide the necessaryultrasonic energy or RF energy modalities at the respective outputs ofthe generator 500 labelled (ENERGY1/RETURN) and (ENERGY2/RETURN).

The tissue treating portion of the ultrasonic blade 149 is configured toapply ultrasonic energy to tissue to affect treatment of the tissue andthe ultrasonic amplitude of the tissue treating portion is controlled bythe processor 502. The at least one electrode is configured to receiveRF energy from the generator 500 output and to apply the RF energy tothe tissue via the electrode. The amplitude of the electrosurgical RFenergy is controlled by the processor 502. In one aspect, the tissuereaction determination corresponds to a boiling point of fluid in thetissue. Moreover, the processor 502 may be configured to generate atarget impedance trajectory as a function of the measured tissueimpedance and a predetermined desired rate of change of tissueimpedance, and the tissue reaction determination. The target impedancetrajectory includes a plurality of target impedance values for each of aplurality of points of time. Furthermore, the processor 502 may beconfigured to drive tissue impedance along the target impedancetrajectory by adjusting the ultrasonic amplitude of the tissue treatingportion of the ultrasonic blade 149 to substantially match the tissueimpedance to a predetermined tissue impedance value for a predeterminedtime period.

Also disclosed herein are control processes for dynamically changing theenergy delivered from a generator based on tissue impedance of tissueengaged with an end effector, such as an end effector of a surgicalinstrument 108. According to one aspect, a process for controlling thepower output from a generator, such as the generator 500 of FIG. 8, thatis delivered to the end effector 125 of the surgical instrument 108 caninclude an input that represents tissue impedance of tissue engaged withthe end effector 125 of the surgical instrument 108. During the tissuetreatment process, the energy profile from the generator 500 can bedynamically changed between RF energy and ultrasonic energy based on thetissue impedance. This allows the generator 500 to switch from RF energyto ultrasonic energy based on the tissue impedance of the tissue undertreatment. The tissue impedance is related to the creation of a propercoagulation seal, for example, when RF energy is delivered from thegenerator 500 to the end effector 125 of the surgical instrument 108,such that RF energy should be used when there is sufficient tissueimpedance. Thus, in one aspect, when a particular tissue impedance isnot found and there is not a sufficient tissue impedance to activate aRF energy modality on the tissue for proper coagulation or seal,ultrasonic energy may be delivered to the end effector 125 to raise thetissue impedance to a level where the RF energy modality can bedelivered to complete the seal.

Energy parameters are configured to be loaded into the generator 500,and can include a plurality of different parameters, including but notlimited to voltage, current, power, and one or more processes for use intreating tissue. These parameters can be related to the RF energy andultrasonic energy that can be delivered from the generator 500 andaccordingly, may be based on tissue impedance of tissue engaged with asurgical device. The energy parameters can include information such asmaximum and/or minimum values to be used to control the energy deliveredfrom the generator 500. The energy parameters can be stored in a varietyof locations, including an EEPROM on the surgical instrument 108 or someother non-volatile memory. In addition, there can be multiple sets ofenergy parameters. For example, there can be a first set of energyparameters that are used to optimize tissue transection, and a secondset of energy parameters that are used to optimize tissue spotcoagulation. It will be understood that there can be any number of setof energy parameters that correspond to various types of tissuetreatments to allow the generator to switch between the various sets ofenergy parameters based on the necessary tissue treatments.

It will be understood that various combinations of information can beused to determine which set of energy parameters are to be used duringtissue treatment. For example, the aperture of the end effector andcalculated tissue impedance can be used to determine which set of energyparameters are needed to control the energy being delivered from thegenerator.

In another aspect, a process for controlling the power output from agenerator, such as the generator of FIG. 8, that is delivered to the endeffector of the surgical instrument can include an input that includesinputs related to the size of the tissue being treated by the endeffector of the surgical instrument. The energy being delivered from thegenerator can be dynamically changed during the procedure between RF andultrasonic energy to achieve dissection and coagulation of a largetissue based on a determination of the effectiveness of the RF energy incoagulating the large tissue. A determination of the effectiveness ofthe RF energy in coagulating a tissue includes a calculation of tissueimpedance, as explained above, of the large tissue interacting with theend effector, which is used to determine the type of energy beingdelivered by the generator to the end effector.

Technique for Switching Between RF and Ultrasonic Energy Based on TissueImpedance

In one aspect, the present disclosure provides techniques for switchingbetween RF and ultrasonic energy based on tissue impedance. The poweroutput from a generator, such as the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), is delivered to an end effector of a surgicalinstrument can be controlled based on the tissue impedance. The energyprofile of the power output of the generator is dynamically switchedbetween RF and ultrasonic energy modalities based on the tissueimpedance to treat the tissue clamped between a clamp jaw and anultrasonic blade of the end effector of the surgical instrument. Forconciseness and clarity of disclosure, the techniques for switchingbetween RF and ultrasonic energy based on tissue impedance will bedescribed with reference to the surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

The following description provides techniques for measuring tissueimpedance and dynamically switching the energy profile of the generatorbetween RF and ultrasonic energy modalities based on the tissueimpedance during the procedure. To provide a better seal, it may bedesirable to operate a “combination” RF/ultrasonic instrument 108 suchthat the instrument transition from a tissue coagulation mode to atissue cut mode during an application of the instrument 108 on tissue.Disclosed is a way to automatically transition from the RF (coagulationor seal) mode to the ultrasonic (cut or transection) mode. In various RFsealing techniques, the RF energy is applied with the goal of drivingthe tissue impedance to a particular level, called the “termination”impedance. It has been demonstrated that an adequate seal is achieved ifan RF sealing technique is able to drive the tissue impedance to thistermination impedance.

In order to determine the tissue impedance being treated by the endeffector 125 of the surgical instrument 108, the tissue impedance mustbe calculated. The calculated tissue impedance is compared to athreshold value, as will be discussed in more detail below. Thecalculated tissue impedance is used by a technique to control the energybeing delivered from the generator 500 to the surgical instrument 108 toallow the energy to switch between RF and ultrasonic energy when thetissue impedance reaches the threshold level. In one form, the tissueimpedance is described by dividing the voltage measurement by thecurrent measurement. More generally, impedance is the ratio of thevoltage vector and the current vector and results in a complex numberwith the real component R and the imaginary component X dependent onboth tissue properties and the frequency and spectra of the appliedstimulus. This number also can be expressed in the form of a magnitude,|Z| and phase ϕ. Most calculations of tissue impedance ignore the smallcontribution of the phase difference between the voltage and current andpresume that the magnitude of the impedance vector |Z| is essentiallyequivalent to the real component of the impedance, R. For purposes ofdescription, the term R and Z indicating tissue impedance will be usedinterchangeably though it should be noted that sensing of tissueimpedance implies that the impedance vector is the general form and anycombination of magnitude, phase, real and imaginary components of thisvector for determining tissue properties, control of energy delivery andthe like is implied by this disclosure.

For example, when utilizing the surgical instrument 108 that canautomatically transition between RF and ultrasonic energy, RF energy canbe applied to the tissue utilizing the end effector 108 to drive thetissue impedance of the tissue to a particular level, such as atermination impedance. The termination impedance is the tissue impedancelevel of the tissue that substantially ensure that the RF energy hasachieved adequate coagulation of the tissue.

FIG. 89 is a graphical depiction of a tissue impedance function 6200represented as tissue impedance |Z| (Ohms) as a function of time (Sec)and showing a termination impedance at which a proper tissue seal isachieved utilizing RF energy. The tissue impedance function 6200 showsthe termination impedance Z_(T) 6216 at which a proper tissue seal isachieved utilizing RF energy. Time in seconds is shown along thehorizontal axis and impedance in Ohms is shown along the vertical axis.The tissue impedance function 6200 can be described in three sections.In section one 6202, the tissue impedance function 6200 represents theinitial impedance 6208 of the tissue from a time just after RF energy isapplied to the tissue to a time when the tissue impedance drops to aminimum value as shown in the section two 6204. In section one 6202 ofthe tissue impedance function 6200, the tissue impedance drops from aninitial value 6208 and decreases, e.g., has a negative slope, until itreaches a first inflection point 6210 and stabilizes to a minimumimpedance 6212 in the second section 6204 of the tissue impedancefunction 6200 where the tissue impedance function flattens 6200 flattensout. After energy is applied to the tissue for a certain period (e.g.,4.5 seconds as shown) the moisture content of the tissue evaporatescausing the tissue to dry out and causes the tissue impedance to beginrising, e.g., positive slope, at a second inflection point 6214 insection three 6206 of the tissue impedance function 6200 until thetissue impedance reaches a predetermined termination impedance 6216, atwhich point in time the RF energy to the end effector is shut off. Thelast portion 6218 of the tissue impedance function 6200 in section three6206 (shown in dashed line) represents the increase in tissue impedanceZ that would result if the RF energy were to be applied continuouslyinstead of being shut off at the termination impedance 6216 point. Thetissue impedance function 6200 may be referred to as the “bathtub” zonein a tissue sealing process due to its characteristic shape.

Once the termination impedance 6216 is reached, the generator 500 canswitch from delivering RF energy to delivering ultrasonic energy to theend effector 125. The termination impedance 6216 can be a fixed valuebased on the electrode and compression properties or it can be avariable that depends on factors measured during the grasping andcoagulation cycle such as amount of tissue grasped, initial impedance,and minimum impedance. It also can be a variable dependent on variousslopes of impedance, energy delivery at various points in thecoagulation cycle such as minimum impedance, and/or inflection points,and combinations thereof.

FIG. 90 is a logic flow diagram 6300 to control the generator 500 toswitch between RF and ultrasonic energy upon reaching a predeterminedtermination impedance. As described herein, the logic flow diagram 6300may be implemented in the generator 500, the surgical instrument 108, ora combination thereof. With reference now to the logic flow diagramshown in FIG. 90, the processor 502 determines the tissue impedance asdescribed herein. For example, the processor 502 may determine thetissue impedance by dividing the output of the second voltage sensingcircuit 524 coupled across the terminals labeled ENERGY2/RETURN by theoutput of the current sensing circuit 514 disposed in series with theRETURN leg of the secondary side of the power transformer 508 as shownin FIG. 8. Initially, the end effector 125 of the surgical instrument108 is closed 6302 on the tissue and the end effector 125 is activatedwith RF energy from the generator 500. A technique for controlling theRF energy being delivered from the generator 500 to the tissue isapplied 6304 to effect a tissue seal using the RF energy. This techniquemay comprise selecting and applying composite load curves (CLC) tablesby the processor 502 of the generator 500, as described in connectionwith FIG. 64 hereinbelow. The processor 502 compares 6306 the tissueimpedance to a threshold value to determine if the tissue impedance hasreached the termination impedance at which time the generator 500 canswitch from RF energy for coagulating or sealing tissue to ultrasonicenergy for cutting tissue. Until the termination impedance is reached,the processor 502 proceeds along the NO branch to and signals thewaveform generator 540 or amplifier 506 to continue delivering 6304 RFenergy to the end effector 125. When the termination impedance isreached, the processor 502 proceeds along the YES branch and signals thewaveform generator 504 or amplifier 506 to stop delivering RF energy(ENERGY2/RETURN) and the switch 6308 to delivering ultrasonic energy(ENERGY1/RETURN). Upon completing the tissue cut utilizing ultrasonicenergy, the tissue is released 6310 from the end effector 125.

FIGS. 91A and 91B illustrate example graphs of the energy, both RF andultrasonic, that is delivered to an end effector 125 of a surgicalinstrument 108 from a generator 500. The technique as described hereincan be used to control the RF and ultrasonic energy to automaticallyswitch from RF to ultrasonic energy to perform tissue cutting. Acombined RF and ultrasonic surgical instrument 108 would then use atechnique graphically depicted in FIGS. 91A and 91B to deliver andcontrol RF energy to the electrodes in the end effector 125. At the endof the termination pulses 6406 (FIG. 91A), the generator 500 canautomatically switch over to the ultrasonic mode to perform the tissuecutting.

In particular, FIG. 91A is a graphical depiction 6400 of a generator RFpower 6402 function and RF tissue impedance function 6404 represented asfunctions of time. The RF power function 6402 is delivered from agenerator 500 to an end effector 125 of a surgical instrument 108. Power(Joules) is shown along the left vertical axis, tissue impedance (Ohms)is shown along the right vertical axis, and time (Seconds) is shownalong the horizontal axis. FIG. 91B is a graphical depiction 6450 of aRF voltage function 6452 and a RF current function 6454 represented asfunctions of time. The RF voltage and current functions 6452, 6454coincide with the RF power and impedance functions 6402, 6404 deliveredfrom the generator 500 to the electrodes in the end effector 125 of thesurgical instrument 108. RF voltage (V) is shown along the left verticalaxis, RF current (mA) is shown along the right vertical axis, and time(Seconds) is shown along the horizontal axis. Although the graphicaldepictions 6400, 6450 of the RF power function 6402 and the RF tissueimpedance function 6404 and the RF voltage and RF current functions6452, 6454 are shown in two separate graphs, it will be appreciated thatall four functions 6402, 6404, 6452, 6454 occur simultaneously inresponse to the tissue impedance and techniques executed by the controlcircuits of the generator 500.

The graphical depiction 6400 of the RF power function 6402, the RFtissue impedance function 6404, the RF voltage function 6452, and the RFcurrent function 6454 are divided into three separate modes. In Mode 1,the generator 500 delivers the RF power function 6402 to the electrodesin contact with the tissue clamped between the clamp jaw 145 and theultrasonic blade 149 of the end effector 125. In Mode 1, the tissueimpedance is low and demands high RF current 6454 from the generator500. Thus, as the RF current 6452 is pulsed the RF voltage 6454 dropsbelow its nominal output level. While the RF power 6402 is delivered tothe tissue, the generator 500 enters Mode 2 where the control circuitmanages the RF power 6402 delivered to the tissue to effect a properseal. In one aspect, during Mode 2, the process includes selecting andapplying CLC tables by the processor 502 of the generator 500, asdescribed in connection with FIG. 64 hereinbelow. As the RF powerfunction 6402 is applied to the tissue in Modes 1 and 2, the tissuebegins to seal and moisture is evaporated for the tissue due to the heatgenerated in the process causing the tissue impedance to increase. Thisis known as the “bathtub” zone, as previously described in connectionwith the tissue impedance function 6200 in FIG. 89. Back to FIG. 91B,the generator 500 enters Mode 3 when the tissue impedance reaches atermination impedance 6406 of the RF tissue impedance function 6404. InMode 3, the processor 502 signals the waveform generator 504 to employRF energy to measure the tissue impedance and to use ultrasonic energyto the ultrasonic blade 149 to cut the tissue. Non-therapeutic RF powerfunction 6402 may be applied to the tissue to measure the tissueimpedance during the ultrasonic cutting phase in Mode 3.

FIG. 91C is a graphical depiction 6475 of the power function 6402,impedance function 6404, voltage function 6452, and current function6453 as a function of time delivered from a generator to an end effectorof a surgical instrument as shown in FIGS. 91A and 91B.

Simultaneous Control Techniques for Combination Ultrasonic/RF SurgicalInstrument

In one aspect, the present disclosure provides a technique forcontrolling the power output from a generator, such as the generators102, 200, 300, 400, 500 (FIGS. 1-3 and 4-8). The power delivered to anend effector of a surgical instrument can include simultaneousactivation of RF and ultrasonic energy modalities to treat the tissueclamped between a clamp jaw and an ultrasonic blade of the end effectorof the surgical instrument. For conciseness and clarity of disclosure,the techniques for simultaneously activating RF and ultrasonic energymodalities will be described with reference to the surgical instrument108 of FIG. 2 coupled to the generator 500 of FIG. 8, although it willbe appreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

The following description provides techniques for simultaneousactivation of RF and ultrasonic energy modalities to treat the tissueclamped between a clamp jaw and an ultrasonic blade of the end effectorof the surgical instrument. For conciseness and clarity of disclosure,the simultaneous application of different energy modalities will bedescribed with reference to the surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

There are many benefits to a surgical instrument 108 that is capable ofdelivering both RF and ultrasonic energy. By having both modalities inone instrument 108, the instrument 108 is able to create stronger sealsand also cut without the need for a separate knife. The followingdisclosure provides multiple simultaneous energy delivery techniquesthat could be used for sealing various vessels.

In general, the present disclosure provides a surgical instrument 108and generator 500 capable of simultaneous activation of both RF andultrasonic energy modalities. The simultaneous activation of both RF andultrasonic energy modalities may be implemented utilizing a singlegenerator capable of delivering both energy modalities from two or moreports, two separate generators, or a single port generator 500 capableof delivering both RF and ultrasonic energy modalities via a singleport. Multiple configurations of the simultaneous techniques aredisclosed. In one aspect, a technique utilizes CLC tables to implementan RF sealing technique while the ultrasonic energy is activated at aconstant power level. Accordingly, the RF CLC tables are activated atthe same time that ultrasonic energy is delivered. In one aspect, thetechnique selects and applies the CLC tables process according to FIG.81.

During a seal only mode, the activation of power for both RF andultrasonic energies are terminated at the point at which the RFtermination impedance is reached, therefore, preventing the risk ofinadvertently cutting through the tissue. One advantage of simultaneousactivation of RF and ultrasonic energy modalities is that the ultrasonicenergy heats up the ultrasonic blade 149 and helps to create a reductionin the difference in thermal mass between the ultrasonic blade 149 andthe electrode.

In particular, FIG. 92 is a logic flow diagram 6500 of one aspect of aprocess of applying simultaneous activation of different energymodalities to tissue. As described herein, the logic flow diagram 6500may be implemented in the generator 500, the surgical instrument 108, ora combination thereof. With reference now to the logic flow diagram6500, tissue is clamped between the clamp arm 145 and the ultrasonicblade 149 of the end effector 125 of the surgical instrument 108 andthen the generator 500 applies the simultaneous energy modalities. TheRF energy delivery process 6502 is shown on the left side of the logicflow diagram 6500 and the ultrasonic energy delivery process 6512 isshown on the right. Once the tissue is clamped between the clamp jaw 145and the ultrasonic blade 149, the processor 502 signals the waveformgenerator 504 to activate 6504 the RF energy and to activate 6514 theultrasonic energy at a constant power level. Once the RF energy isactivated 6504 the processor 502 signals the waveform generator 504 todeliver 6506 RF sealing techniques and to maintain 6516 the ultrasonicenergy at a constant power level activation. In one aspect, the RFsealing techniques applied by the generator 500 involve selecting andapplying the CLC tables according to the process described in FIG. 81.Referring back to FIG. 92, during the application 6506 of the RF sealingtechniques, the processor 502 monitors the tissue impedance anddetermines when the termination impedance is reached. When thetermination impedance is reached 6508, feedback is signaled 6518 to theprocessor 502 to terminate the ultrasonic power delivery. Subsequently,the processor 502 signals the waveform generator 504 to terminate 6510the RF power and to terminate 6520 the ultrasonic power. As previouslydiscussed, the processor 502 measures the RF tissue impedance bydividing the output of the second voltage sensing circuit 524 by theoutput of the current sensing circuit 514.

FIG. 93 is a graphical depiction 6600 of an RF tissue impedance function6602 represented as RF tissue impedance (Ohms) as a function of time(Sec) in connection with the logic flow diagram 6500 of FIG. 92 toillustrate first and second termination impedances. As previouslydescribed, one advantage of simultaneous activation of RF and ultrasonicenergy modalities is that the ultrasonic energy heats up the blade andhelps to create a reduction in the difference in thermal mass betweenthe blade and the electrode. In the graphical depiction 6600 of FIG. 93,the horizontal axis is time (ms) and the vertical axis is RF tissueimpedance (Ohms). The first portion 6604 of the RF tissue impedancefunction 6602 coincides with the application of the RF energy sealingprocess described in connection with FIG. 64 and the constant ultrasonicpower. The tissue impedance is monitored during the tissue sealingprocess utilizing the RF energy. When the tissue impedance reaches afirst termination impedance 6606, the ultrasonic power is terminated andwhen the tissue impedance reaches a second termination impedance 6608the RF power is terminated to avoid cutting through the sealed tissue.

FIG. 94 illustrates an example of the quality of a seal 6702 made in avessel 6700 utilizing simultaneous activation of RF and ultrasonicenergy modalities as described in connection with FIGS. 92 and 93. Themain advantage of simultaneous activation of RF and ultrasonic energymodalities is that the ultrasonic energy heats up the ultrasonic blade149 and helps to create a reduction in the difference in thermal massbetween the ultrasonic blade 149 and the electrode in the clamp arm 145.During a non-simultaneous activation seal cycle utilizing both RF andultrasonic modalities, a challenge is posed to create a strong seal withvarying thermal masses on either side of the end effector 125 jaw. Theboxplots shown in FIGS. 95 and 96 below demonstrate the tissue effectadvantages mentioned above (simultaneously heating the ultrasonic blade149 and electrode) of activating a simultaneous energy modalitytechnique.

FIG. 95 is a boxplot graphic 6800 comparison of the burst pressure of acarotid artery seal made utilizing: (1) simultaneous application of RFand ultrasonic energy and (2) application of RF energy only as describedin connection with FIGS. 92-94. Energy modality is shown along thehorizontal axis and burst pressure (mmHg) of the two carotid arteryseals represented by first and second boxplots 6802, 6804 is shown alongthe vertical axis. Along the horizontal axis, the first boxplot 6802represents a carotid artery seal made utilizing simultaneousRF/ultrasonic energy and the second boxplot 6804 represents a carotidartery seal made utilizing RF energy only. The first and second boxplots6802, 6804 demonstrate the tissue effect advantages provided by thesimultaneous application of RF/ultrasonic energy modality as depicted bythe logic flow diagram 6500 of FIG. 92 where simultaneously heating theultrasonic blade 149 and electrode provides the high quality tissue seal6702 shown in FIG. 94.

FIG. 96 is a boxplot graphic 6900 comparison of the burst pressure of acarotid artery bundle seal made utilizing: (1) simultaneous applicationof RF and ultrasonic energy and (2) application of RF energy only asdescribed in connection with FIGS. 92-94. Energy modality is shown alongthe horizontal axis and burst pressure (mmHg) of the two carotid arterybundle seals represented by first and second boxplots 6902, 6904 isshown along the vertical axis. Along the horizontal axis, the firstboxplot 6902 representing a carotid artery bundle seal made utilizingsimultaneous RF/ultrasonic energy and the second boxplot 6904 representsa carotid artery bundle seal made utilizing RF energy only. The firstand second boxplots 6902, 6904 demonstrate the tissue effect advantagesprovided by the simultaneous application of RF/ultrasonic energymodality as depicted by the logic flow diagram 6500 of FIG. 92 wheresimultaneously heating the ultrasonic blade 149 and electrode providesthe high quality tissue seal 6702 shown in FIG. 94.

FIG. 97 is a boxplot graphic 7000 comparison of the burst pressure of athyrocervical artery seal made utilizing: (1) simultaneous applicationof RF and ultrasonic energy and (2) application of RF energy only asdescribed in connection with FIGS. 92-94. Energy modality is shown alongthe horizontal axis and burst pressure (mmHg) of the two thyrocervicalartery seals represented by first and second boxplots 7002, 7004 isshown along the vertical axis. Along the horizontal axis, the firstboxplot 7002 represents a thyrocervical artery seal made utilizingsimultaneous RF/ultrasonic energy and the second boxplot 7004 representsa thyrocervical artery seal made utilizing RF energy only. The first andsecond boxplots 7002, 7004 demonstrate the tissue effect advantagesprovided by the simultaneous application of RF/ultrasonic energymodality as depicted by the logic flow diagram 6500 of FIG. 92 wheresimultaneously heating the ultrasonic blade 149 and electrode providesthe high quality tissue seal 6702 shown in FIG. 94.

There are several factors that can drive the simultaneous RF/ultrasonicenergy application technique. Ultrasonic power level is a factor if a“seal only” configuration is desired. For example, a lower ultrasonicpower level may be selected as not to cut through the tissue. Datasuggests that the higher the ultrasonic power level, the greater theseal results as shown and described below in connection with FIG. 98. Inparticular, FIG. 98 is a boxplot graphic 7100 comparison of the burstpressure of a carotid artery bundle seal made utilizing simultaneousapplication of: (1) RF and lower ultrasonic energy and (2) RF energy andhigher ultrasonic energy as described in connection with FIGS. 92-94.Ultrasonic power level is shown along the horizontal axis and burstpressure (mmHg) of the two carotid artery bundle seals represented byfirst and second boxplots 7102, 7104 is shown along the vertical axis.Along the horizontal axis, the first boxplot 7102 represents a carotidartery bundle seal made utilizing simultaneous RF energy and lowerultrasonic energy and the second boxplot 7104 represents a carotidartery bundle seal made utilizing RF energy and lower ultrasonic energyrelative to the first boxplot 7102. The first and second boxplots 7102,7104 demonstrate that the higher the ultrasonic power level, the greaterthe seal.

If a “seal and cut” configuration is desired, a higher ultrasonic powerlevel may be selected as an option to seal and cut tissue moreefficiently with great tissue effects. Additionally, ultrasonic powerlevel can also be altered during the seal/transection cycle based on theRF tissue impedance feedback. During a seal and cut cycle, the RF tissueimpedance can be monitored and ultrasonic power delivered based on RFfeedback impedance. There are different points during a seal in whichimpedance readings are useful including, for example, terminationImpedance and power pulse impedance.

In regard to the termination impedance, one of which is the terminationimpedance which occurs as the impedance rises out of the sealing zone6604 at a steady rate, as shown in FIG. 93. In particular, FIG. 99 is aboxplot graphic 7200 comparison of the burst pressure of a carotidartery bundle seal made utilizing simultaneous application of RF andultrasonic energy at different termination impedances as described inconnection with FIGS. 92-94. Termination impedance (Ohms) is shown alongthe horizontal axis and burst pressure (mmHg) of the two carotid arterybundle seals represented by first and second boxplots 7202, 7204 isshown along the vertical axis. Along the horizontal axis, the firstboxplot 7202 represents a carotid artery bundle seal made utilizingsimultaneous application of RF energy and ultrasonic energy terminatedat a termination impedance of 1000 Ohms and the second boxplot 7204represents a carotid artery bundle seal made utilizing simultaneousapplication of RF energy and ultrasonic energy terminated at atermination impedance of 2000 Ohms. The first and second boxplots 7202,7204 demonstrate that the higher the termination impedance, the greaterthe seal. Thus, termination impedance is a statistical factor in thebundle tissue model for burst pressure as it yielded greater burstpressure results.

The power pulse impedance threshold is another point at which thesealing process could be optimized. This is the point at which the powerpulse of the CLC tables delivers the most energy into the tissue. Itmonitors the point at which the impedance threshold is reached to knowwhen the tissue has reached the state to begin the termination pulses.Changing the impedance value of the power pulse (lower value) can enablefaster seal times with the same great burst pressure results.

Modulation Techniques for Ultrasonic Energy in Seal Only and Seal andCut Modes

In one aspect, the present disclosure provides techniques for modulatingultrasonic energy in seal only mode and seal and cut mode. The poweroutput from a generator, such as the generators 102, 200, 300, 400, 500(FIGS. 1-3 and 4-8), is controlled to modulate ultrasonic energy in sealonly mode and seal and cut mode. The ultrasonic energy delivered to anend effector of a surgical instrument can be modulated to provide “sealonly” mode or “seal and cut” mode to treat the tissue clamped between aclamp jaw and an ultrasonic blade of the end effector of the surgicalinstrument. For conciseness and clarity of disclosure, the techniquesfor modulating ultrasonic energy in seal only mode and seal and cut modewill be described with reference to the surgical instrument 108 of FIG.2 coupled to the generator 500 of FIG. 8, although it will beappreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

The following description provides techniques for modulating ultrasonicenergy in seal only and seal and cut modes to treat the tissue clampedbetween a clamp jaw and an ultrasonic blade of the end effector of thesurgical instrument. For conciseness and clarity of disclosure, thesimultaneous application of different energy modalities will bedescribed with reference to the surgical instrument 108 of FIG. 2coupled to the generator 500 of FIG. 8, although it will be appreciatedthat other configurations of instruments, generators, and end effectorsdescribed herein may be readily substituted without departing from thescope of the present disclosure.

In general, a surgical instrument 108 configured with a “seal only” modeand a “seal and cut” mode provide the surgeons the option of sealing orsealing and cutting tissue based on their intended surgical task. In oneaspect, the surgical instrument 108 is configured to utilize both RF andultrasonic technology in combination to achieve this task. In oneaspect, in a “seal only” mode, the generator 500 is configured todetermine when a cut is complete to eliminate a partial transection 7304as shown in FIG. 100 below. An example of a vessel with a quality vesselseal made utilizing simultaneous application of RF and ultrasonic energyis shown FIG. 99. In particular, FIG. 100 is an example of a vessel 7360with a partial seal 7302 made utilizing simultaneous application of RFand ultrasonic energy and a partial transection 7304 made utilizingultrasonic energy.

Accordingly, it is desirable to provide “seal only” and “seal and cut”techniques utilizing RF and ultrasonic energy modalities to optimize thequality of seal and a seal and cut operation. In one aspect, a “sealonly” technique may be applied as graphically depicted in FIG. 101. Theseal only technique delivers simultaneous energy of ultrasonic and RFfor the duration of the seal. The seal only technique can be optimizedby modulating the ultrasonic energy delivered based on the RF tissueimpedance.

In particular, FIG. 101 is a graphical depiction 7400 of an RF tissueimpedance function 7402 represented as RF tissue impedance (Ohms) as afunction of time (Sec) and an ultrasonic current function 7404represented as ultrasonic current (mA) as a function of time (Sec)during a “seal only” modality. Time (Sec) is shown along the horizontalaxis, impedance (Ohms) is shown along the left vertical axis, andultrasonic current (mA) is shown along the right vertical axis. The“seal only” modality is achieved in three separate stages. During afirst stage 7406, only RF energy is delivered to the electrodes and theultrasonic current function 7404 is zero. During the first stage 7406,the impedance is slightly above zero such that power can be delivered tothe tissue. At the end of the first stage 7406 and marking the beginningof the second stage 7408, the ultrasonic energy is delivered to theultrasonic blade 149 in conjunction with the RF energy. During thesecond stage 7408, the ultrasonic current 7414 remains constant at ˜200mA and the impedance begins to slowly increase as the tissue driesduring the sealing process. Once the inflection point 7412 of theimpedance function 7402 is reached, at the end of the second stage 7408marking the beginning of the third stage 7410, the impedance starts torapidly increase. The impedance is fed back to the generator 500 andwhen the impedance is equal to or greater than the inflection point 7412impedance, the generator 500 decrements the ultrasonic current to reducethe amount of ultrasonic energy applied to the tissue to avoid cuttingthe tissue and achieve the seal only modality. During the third stage7410, the ultrasonic current is decremented by equal steps 7416, asshown in FIG. 101, until the seal is complete, but without cutting thetissue. In other aspects, the ultrasonic current may be decremented byvariable and non-equal steps 7416. In one aspect the decrement value is˜50 mA, and thus the first decremented current value is ˜150 mA. Whenthe impedance reaches a termination impedance, both the RF andultrasonic power are turned off.

FIG. 102 is logic flow diagram 7500 of one aspect of a technique forsimultaneous activation of RF and ultrasonic energy and modulating theultrasonic energy to achieve a seal only process. As described herein,the logic flow diagram 7500 may be implemented in the generator 500, thesurgical instrument 108, or a combination thereof. With reference to thegraphical depiction 7400 of FIG. 101 and in accordance with the logicflow diagram 7500 of FIG. 102, the processor 502 signals the waveformgenerator 504 to deliver 7502 RF energy to the end effector 125 (e.g.,to the electrode) for a first period during the first stage 7406 of theseal only process. At the end of the first period, the processor 502signals the waveform generator 504 to deliver 7504 ultrasonic energy tothe end effector 125 (e.g., to the ultrasonic blade 149) for a secondperiod during the second stage 7408 of the seal only process. Theprocessor 502 monitors 7506 the RF tissue impedance and compares 7508the RF tissue impedance to a predetermined impedance corresponding tothe inflection point 7412 impedance of the impedance function 7402 asshown in FIG. 101. If the RF tissue impedance is less than thepredetermined inflection point 7412 impedance (“inflection impedance”),near the end of the sealing stage where the impedance begins to rapidlyrise, the processor 502 proceeds along the NO branch and continues tomonitor 7506 the RF tissue impedance while RF energy and constantultrasonic energy is delivered 7502, 7504 to the end effector 125 duringthe second stage 7408 of the seal only process. As previously discussed,the processor 502 measures the RF tissue impedance by dividing theoutput of the second voltage sensing circuit 524 by the output of thecurrent sensing circuit 514.

When the RF tissue impedance is equal to or greater than the inflectionimpedance, the process proceeds along the YES branch and the processor502 signals the waveform generator 504 to reduce 7510 the ultrasonicenergy from a first power level to a second power level by apredetermined decrement (˜50 mA, or any suitable or desired value). Theultrasonic energy may be reduced by a discrete reduction of a numericalquantity or may be reduced by a continuous quantity. In one aspect, the˜200 mA ultrasonic current delivered during the second stage 7408 isdecreased by a ˜50 mA step to ˜150 mA, to minimize the risk of partiallytransecting or cutting the vessel and achieve the seal only modality.The processor 502 compares 7512 the RF tissue impedance to apredetermined termination impedance. If the RF tissue impedance is lessthan the termination impedance, the processor 502 proceeds along the NObranch and the ultrasonic current function 7404 is reduced 7510 by thepredetermined step, which can be done in equal or variable steps. Whenthe RF tissue impedance is equal to or greater than the terminationimpedance, the processor 502 proceeds along the YES branch and thegenerator 500 terminates 7514 both the RF and ultrasonic energy. Themodulated ultrasonic current function 7404 shown in FIG. 101 enables theachievement of a “seal only” modality without the risk of a partialtransection. The technique can be store as a logic function or series ofcomputer executable instructions in a look-up table in memory, such asan EEPROM located on the surgical instrument 108 or the generator 500.

In particular, FIG. 103 is a graphical depiction 7600 of an RF tissueimpedance function 7602 represented as RF tissue impedance (Ohms) as afunction of time (Sec) and an ultrasonic current function 7404represented as ultrasonic current (mA) as a function of time (Sec)during a “seal and cut” modality. Time (Sec) is shown along thehorizontal axis, impedance (Ohms) is shown along the left vertical axis,and ultrasonic current (mA) is shown along the right vertical axis. The“seal and cut only” modality is achieved in three separate stages.During a first stage 7606, only RF energy is delivered to the electrodesand the ultrasonic current function 7604 is zero. During the first stage7606, the impedance is slightly above zero such that power can bedelivered to the tissue. At the end of the first stage 7606 and markingthe beginning of the second stage 7608, the ultrasonic energy isdelivered to the ultrasonic blade 149 in conjunction with the RF energy.During the second stage 7608, the ultrasonic current 7614 remainsconstant at ˜200 mA and the impedance begins to slowly increase as thetissue dries during the sealing process. Once the inflection point 7612of the impedance function 7602 is reached, at the end of the secondstage 7608 marking the beginning of the third stage 7610, the impedancestarts to rapidly increase. The impedance is fed back to the generator500 and when the impedance is equal to or greater than the inflectionpoint 7612 impedance, the generator 500 increments the ultrasoniccurrent to increase the amount of ultrasonic energy applied to thetissue to achieve the seal and cut modality. During the third stage7610, the ultrasonic current is incremented in equal steps 7616, asshown in FIG. 103, until the seal and cut is achieved. In other aspects,the ultrasonic current may be incremented by variable and non-equalsteps. In one aspect the increment step 7616 value is ˜50 mA, and thusthe first incremented current value is ˜150 mA. When the impedancereaches a termination impedance indicating that the cut is complete,both the RF and ultrasonic power are turned off.

FIG. 104 is a logic flow diagram 7700 of one aspect of a technique forsimultaneous activation of RF and ultrasonic energy and modulating theultrasonic energy to achieve a seal and cut process. As describedherein, the logic flow diagram 7700 may be implemented in the generator500, the surgical instrument 108, or a combination thereof. Withreference to the graphical depiction 7600 of FIG. 103 and in accordancewith the logic flow diagram 7700 of FIG. 104, the processor 502 signalsthe waveform generator 504 to deliver 7702 RF energy to the end effector125 (e.g., to the electrode) for a first period during the first stage7606 of the seal and cut process. At the end of the first period, theprocessor 502 signals the waveform generator 504 to deliver 7704ultrasonic energy to the end effector 125 (e.g., the ultrasonic blade149) for a second period during the second stage 7608 of the seal andcut process. The processor 502 monitors 7706 the RF tissue impedanceduring a sealing portion of the seal and cut process. The processor 502compares 7708 the RF tissue impedance to a predetermined impedancecorresponding to the inflection point 7612 of the impedance function7602. If the RF tissue impedance is less than the predeterminedinflection point 7612 impedance (“inflection impedance”), near the endof the sealing stage where the impedance begins to rapidly rise, theprocessor 502 proceeds along the NO branch and continues to monitor 7706the RF tissue impedance while RF energy and constant ultrasonic energyis delivered 7702, 7704 to the end effector 125 during the second stage7408 of the seal and cut process. As previously discussed, the processor502 measures the RF tissue impedance by dividing the output of thesecond voltage sensing circuit 524 by the output of the current sensingcircuit 514.

When the RF tissue impedance is equal to or greater than the inflectionimpedance, the processor 502 proceeds along the YES branch and signalsthe waveform generator 504 to increase 7710 the ultrasonic energy from afirst power level to a second power level by a predetermined decrement(˜75 mA, or any suitable or desired value). The ultrasonic energy may beincreased by a discrete reduction of a numerical quantity or may beincreased by a continuous quantity. In one aspect, the ˜200 mAultrasonic current is increased to ˜275 mA by a ˜75 mA step to achievethe seal and cut modality. The processor 502 compares 7712 the RF tissueimpedance to a predetermined termination impedance. If the RF tissueimpedance is less than the termination impedance, the processor 502proceeds along the NO branch and the ultrasonic current function 7604 isincreased 7710 by the predetermined step, which can be done in equal orvariable steps. When the RF tissue impedance is equal to or greater thanthe termination impedance, the process proceeds along the YES branch andthe generator 500 terminates 7714 both the RF and ultrasonic energy oncethe seal and cut has been achieved. The modulated ultrasonic currentfunction 7604 shown in FIG. 103 enables the achievement of a “seal andcut” modality. The technique can be store as a logic function or seriesof computer executable instructions in a look-up table in memory, suchas an EEPROM located on the surgical instrument 108 or the generator500.

Techniques for Reducing Displacement of Ultrasonic Blade as a Functionof RF Tissue Impedance

In one aspect, the present disclosure provides techniques to reduceultrasonic blade displacement as a function of RF tissue impedance forRF/Ultrasonic combination surgical instruments. The power output from agenerator, such as the generators 102, 200, 300, 400, 500 (FIGS. 1-3 and4-8), is delivered to an end effector of a surgical instrument and canbe controlled to reduce the displacement of an ultrasonic blade as afunction of RF tissue impedance to treat the tissue clamped between aclamp jaw and an ultrasonic blade of the end effector of the surgicalinstrument. For conciseness and clarity of disclosure, the techniquesfor reducing ultrasonic blade displacement as a function of RF tissueimpedance will be described with reference to the surgical instrument108 of FIG. 2 coupled to the generator 500 of FIG. 8, although it willbe appreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

The following description provides techniques for reducing thedisplacement of an ultrasonic blade as a function of RF tissue impedanceto treat the tissue clamped between a clamp jaw and an ultrasonic bladeof the end effector of the surgical instrument. For conciseness andclarity of disclosure, the simultaneous application of different energymodalities will be described with reference to the surgical instrument108 of FIG. 2 coupled to the generator 500 of FIG. 8, although it willbe appreciated that other configurations of instruments, generators, andend effectors described herein may be readily substituted withoutdeparting from the scope of the present disclosure.

In general, it is desirable to reduce the displacement of the ultrasonicblade 149 as a function of RF tissue impedance. Reduction of theultrasonic blade 149 displacement can prevent prematurely cutting thetissue clamped between the clamp jaw 145 and the ultrasonic blade 149 ofthe end effector 125 if cutting tissue is not desired. In order to decaythe displacement of the ultrasonic blade 149, a rise in RF tissueimpedance can be used as feedback to the generator 500 as is well knownthat RF tissue impedance indicates the state of the tissue. For example,tissue with low impedance (i.e., in the first phase of the tissuesealing process) at current operating pressures indicates that thetissue has not yet been cut because the low impedances indicate thepresence of tissue between the clamp jaw 145 and the ultrasonic blade149 of the end effector 125. In general, there has been a reluctance touse high ultrasonic energy while the tissue is in the first phase ofsealing for fear of cutting the tissue prematurely. Nevertheless, highultrasonic energy is desirable in this phase to facilitate energydelivery to tissue when the RF tissue impedance is too low to driveelectrical power into large bites of tissue.

A simple mathematical relationship between RF tissue impedance (Z) andultrasonic blade displacement controlled by the current I_(h) flowingthrough the ultrasonic transducer can be employed to decay thedisplacement of the ultrasonic blade to zero or similar low value toprevent cutting tissue. A number of mathematical mappings exist toappropriately reduce I_(h) as a function of Z such as neural networks,fuzzy logic, polynomials, radial basis functions, Fourier series, andthe like, because many functions and series have been proven to map anyrelationship when a sufficiently high enough order is used. However,only a few functions exist that have a small number of adjustable gainsthat are intuitive to enable optimization. An intuitive functionalmapping is represented in Equation 9 below:

$\begin{matrix}{I_{h} = \left\{ \begin{matrix}I_{\max} & \forall & {Z < Z_{\min}} \\\frac{I_{\max}\left( {Z^{- n} - Z_{\max}^{- n}} \right)}{\left( {Z_{\min}^{- n} - Z_{\max}^{- n}} \right)} & \forall & {Z_{\min} < Z < Z_{\max}} \\0 & \forall & {Z > Z_{\max}}\end{matrix} \right.} & {{Equation}\mspace{14mu} 9}\end{matrix}$

Where I_(max) is the maximum current the ultrasonic blade can tolerate,Z_(min) is the threshold impedance that dictates when the tissue hasexited the “first phase,” Z_(max) is the impedance at which it isdesired to have I_(h)=0 Amps, and the exponent n dictates the rate ofdecay of the tissue. Both the max and min impedance values can bedynamically updated as a function of the initial Z of the tissue duringenergy onset. A plot of Equation 1 with Z_(max)=500 Ohm, Z_(min)=50 Ohm,and I_(max)=200 mA for various n values is presented in FIG. 105.

In particular, FIG. 105A is a graphical depiction 7800 of an ultrasoniccurrent functions represented as ultrasonic current I_(h) (Amperes)delivered to the ultrasonic transducer as a function of RF tissueimpedance Z (Ohms) for various n values. The horizontal axis is RFtissue impedance Z (Ohms) and the vertical axis is ultrasonic currentI_(h) (Amperes). The first ultrasonic current function 7802 has n=2. Thesecond ultrasonic current function 7804 has n=1. The third ultrasoniccurrent function 7806 has n=−0.25. The fourth ultrasonic currentfunction 7808 has n=−1. The fifth ultrasonic current function 7810 hasn=−3. The sixth ultrasonic current function 7812 has n=−10.

Additionally, FIG. 105B is a graphical depiction 7800′ of another set ofultrasonic current functions represented as ultrasonic current I_(h)(Amperes) delivered to the ultrasonic transducer as a function of RFtissue impedance Z (Ohms) for various n values. The horizontal axis isRF tissue impedance Z (Ohms) and the vertical axis is ultrasonic currentI_(h) (Amperes). The first ultrasonic current function 7802′ has n=0.03.The second ultrasonic current function 7804′ has n=0.04. The thirdultrasonic current function 7806′ has n=0.06. The fourth ultrasoniccurrent function 7808′ has n=0.1.

FIG. 106 is a graphical depiction 7900 of multiple ultrasonic functionsrepresented as functions of time. In particular, FIG. 106 is a graphicaldepiction 7900 of voltage 7902 (V) as a function of time (Sec), current7904 (A) as a function of time (Sec), power 7906 (W) as a function oftime (Sec), and frequency (kHz) as a function of time (Sec), wherevoltage (V) and current (A) are shown along the left vertical axis,power (W) and impedance (Ohm) are shown along the right vertical axis,and time (Sec) is shown along the horizontal axis.

FIG. 107 is a graphical depiction 8000 of constant RF power that wasinputted into Equation 1 with RF energy terminated at 500 Ohm terminalimpedance. In particular, FIG. 107 is a graphical depiction 8000 ofvoltage 8002 (V) as a function of time (Sec), current 8004 (A) as afunction of time (Sec), power 8006 (W) as a function of time (Sec), andimpedance (Ohms) as a function of time (Sec), where voltage (V) andcurrent (A) are shown along the left vertical axis, power (W) andimpedance (Ohm) are shown along the right vertical axis, and time (Sec)is shown along the horizontal axis.

Although the surgical system 100 is independent of the RF techniquebeing applied, for clarity of illustration, a constant RF power wasdelivered to tissue and the ultrasonic current into the ultrasonictransducer was reduced accordingly as shown in FIGS. 106 and 107. Thistechnique achieves a tissue seal without cutting the tissue. In FIG.107, the RF termination impedance was set to 500 Ohms and n=−1. The RFpower delivered (with low risk of cutting tissue) does not need toterminate at the same time that the ultrasonic power is terminated. Postphase one, the RF power heating of tissue improves sealing and cancontinue once ultrasonic power has been shut off. For a given jawpressure and geometry, a surface response design of experiment can beperformed to optimize the parameter values.

While various details have been set forth in the foregoing description,it will be appreciated that the various aspects of the surgical systemwith user adaptable techniques based on tissue type may be practicedwithout these specific details. For example, for conciseness and clarityselected aspects have been shown in block diagram form rather than indetail. Some portions of the detailed descriptions provided herein maybe presented in terms of instructions that operate on data that isstored in a computer memory. Such descriptions and representations areused by those skilled in the art to describe and convey the substance oftheir work to others skilled in the art. In general, a technique refersto a self-consistent sequence of steps leading to a desired result,where a “step” refers to a manipulation of physical quantities whichmay, though need not necessarily, take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It is common usage to refer tothese signals as bits, values, elements, symbols, characters, terms,numbers, or the like. These and similar terms may be associated with theappropriate physical quantities and are merely convenient labels appliedto these quantities.

Unless specifically stated otherwise as apparent from the foregoingdiscussion, it is appreciated that, throughout the foregoingdescription, discussions using terms such as “processing” or “computing”or “calculating” or “determining” or “displaying” or the like, refer tothe action and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

It is worthy to note that any reference to “one aspect,” “an aspect,”“one form,” or “an form” means that a particular feature, structure, orcharacteristic described in connection with the aspect is included in atleast one aspect. Thus, appearances of the phrases “in one aspect,” “inan aspect,” “in one form,” or “in an form” in various places throughoutthe specification are not necessarily all referring to the same aspect.Furthermore, the particular features, structures or characteristics maybe combined in any suitable manner in one or more aspects.

Some aspects may be described using the expression “coupled” and“connected” along with their derivatives. It should be understood thatthese terms are not intended as synonyms for each other. For example,some aspects may be described using the term “connected” to indicatethat two or more elements are in direct physical or electrical contactwith each other. In another example, some aspects may be described usingthe term “coupled” to indicate that two or more elements are in directphysical or electrical contact. The term “coupled,” however, also maymean that two or more elements are not in direct contact with eachother, but yet still co-operate or interact with each other.

Although various forms have been described herein, many modifications,variations, substitutions, changes, and equivalents to those forms maybe implemented and will occur to those skilled in the art. Also, wherematerials are disclosed for certain components, other materials may beused. It is therefore to be understood that the foregoing descriptionand the appended claims are intended to cover all such modifications andvariations as falling within the scope of the disclosed forms. Thefollowing claims are intended to cover all such modification andvariations.

In a general sense, those skilled in the art will recognize that thevarious aspects described herein which can be implemented, individuallyand/or collectively, by a wide range of hardware, software, firmware, orany combination thereof can be viewed as being composed of various typesof “electrical circuitry.” Consequently, as used herein “electricalcircuitry” includes, but is not limited to, electrical circuitry havingat least one discrete electrical circuit, electrical circuitry having atleast one integrated circuit, electrical circuitry having at least oneapplication specific integrated circuit, electrical circuitry forming ageneral purpose computing device configured by a computer program (e.g.,a general purpose computer configured by a computer program which atleast partially carries out processes and/or devices described herein,or a microprocessor configured by a computer program which at leastpartially carries out processes and/or devices described herein),electrical circuitry forming a memory device (e.g., forms of randomaccess memory), and/or electrical circuitry forming a communicationsdevice (e.g., a modem, communications switch, or optical-electricalequipment). Those having skill in the art will recognize that thesubject matter described herein may be implemented in an analog ordigital fashion or some combination thereof.

The foregoing detailed description has set forth various forms of thedevices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof. In one form, severalportions of the subject matter described herein may be implemented viaApplication Specific Integrated Circuits (ASICs), Field ProgrammableGate Arrays (FPGAs), digital signal processors (DSPs), or otherintegrated formats. However, those skilled in the art will recognizethat some aspects of the forms disclosed herein, in whole or in part,can be equivalently implemented in integrated circuits, as one or morecomputer programs running on one or more computers (e.g., as one or moreprograms running on one or more computer systems), as one or moreprograms running on one or more processors (e.g., as one or moreprograms running on one or more microprocessors), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of skill in the art in light of this disclosure.In addition, those skilled in the art will appreciate that themechanisms of the subject matter described herein are capable of beingdistributed as a program product in a variety of forms, and that anillustrative form of the subject matter described herein appliesregardless of the particular type of signal bearing medium used toactually carry out the distribution. Examples of a signal bearing mediuminclude, but are not limited to, the following: a recordable type mediumsuch as a floppy disk, a hard disk drive, a Compact Disc (CD), a DigitalVideo Disk (DVD), a digital tape, a computer memory, etc.; and atransmission type medium such as a digital and/or an analogcommunication medium (e.g., a fiber optic cable, a waveguide, a wiredcommunications link, a wireless communication link (e.g., transmitter,receiver, transmission logic, reception logic, etc.), etc.).

All of the above-mentioned U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications, non-patent publications referred to in this specificationand/or listed in any Application Data Sheet, or any other disclosurematerial are incorporated herein by reference, to the extent notinconsistent herewith. As such, and to the extent necessary, thedisclosure as explicitly set forth herein supersedes any conflictingmaterial incorporated herein by reference. Any material, or portionthereof, that is said to be incorporated by reference herein, but whichconflicts with existing definitions, statements, or other disclosurematerial set forth herein will only be incorporated to the extent thatno conflict arises between that incorporated material and the existingdisclosure material.

One skilled in the art will recognize that the herein describedcomponents (e.g., operations), devices, objects, and the discussionaccompanying them are used as examples for the sake of conceptualclarity and that various configuration modifications are contemplated.Consequently, as used herein, the specific exemplars set forth and theaccompanying discussion are intended to be representative of their moregeneral classes. In general, use of any specific exemplar is intended tobe representative of its class, and the non-inclusion of specificcomponents (e.g., operations), devices, and objects should not be takenlimiting.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations are not expressly set forth herein for sakeof clarity.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely example, and that in fact many other architectures may beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated also can be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated also can be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents, and/or wirelessly interactable, and/or wirelesslyinteracting components, and/or logically interacting, and/or logicallyinteractable components.

In some instances, one or more components may be referred to herein as“configured to,” “configurable to,” “operable/operative to,”“adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Thoseskilled in the art will recognize that “configured to” can generallyencompass active-state components and/or inactive-state componentsand/or standby-state components, unless context requires otherwise.

While particular aspects of the present subject matter described hereinhave been shown and described, it will be apparent to those skilled inthe art that, based upon the teachings herein, changes and modificationsmay be made without departing from the subject matter described hereinand its broader aspects and, therefore, the appended claims are toencompass within their scope all such changes and modifications as arewithin the true spirit and scope of the subject matter described herein.It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to claims containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations.

In addition, even if a specific number of an introduced claim recitationis explicitly recited, those skilled in the art will recognize that suchrecitation should typically be interpreted to mean at least the recitednumber (e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that typically a disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms unless context dictates otherwise. For example, the phrase “Aor B” will be typically understood to include the possibilities of “A”or “B” or “A and B.”

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. Also, although various operational flows are presented in asequence(s), it should be understood that the various operations may beperformed in other orders than those which are illustrated, or may beperformed concurrently. Examples of such alternate orderings may includeoverlapping, interleaved, interrupted, reordered, incremental,preparatory, supplemental, simultaneous, reverse, or other variantorderings, unless context dictates otherwise. Furthermore, terms like“responsive to,” “related to,” or other past-tense adjectives aregenerally not intended to exclude such variants, unless context dictatesotherwise.

Although various forms have been described herein, many modifications,variations, substitutions, changes, and equivalents to those forms maybe implemented and will occur to those skilled in the art. Also, wherematerials are disclosed for certain components, other materials may beused. It is therefore to be understood that the foregoing descriptionand the appended claims are intended to cover all such modifications andvariations as falling within the scope of the disclosed forms. Thefollowing claims are intended to cover all such modification andvariations.

In summary, numerous benefits have been described which result fromemploying the concepts described herein. The foregoing description ofthe one or more forms has been presented for purposes of illustrationand description. It is not intended to be exhaustive or limiting to theprecise form disclosed. Modifications or variations are possible inlight of the above teachings. The one or more forms were chosen anddescribed in order to illustrate principles and practical application tothereby enable one of ordinary skill in the art to utilize the variousforms and with various modifications as are suited to the particular usecontemplated. It is intended that the claims submitted herewith definethe overall scope.

The invention claimed is:
 1. A method comprising: delivering, by a firstdrive circuit, a first energy modality to an end effector of a surgicalinstrument interacting with tissue; determining, by a processor, atissue coefficient of friction of the tissue interacting with the endeffector; comparing, by the processor, the determined tissue coefficientof friction with a threshold value of the tissue coefficient offriction; and delivering, by a second drive circuit, a second energymodality to the end effector when the determined tissue coefficient offriction changes beyond the threshold value of the tissue coefficient offriction; wherein the first energy modality is different from the secondenergy modality.
 2. The method of claim 1, further comprising:controlling, by the processor, the first energy modality delivered tothe end effector based on the tissue coefficient of friction as aninput; and selecting, by the processor, the second energy modality todeliver to interact with the tissue by the end effector, whereinproperties of the first and second energy modalities correspond to atype of interaction between the end effector and the tissue.
 3. Themethod of claim 1, further comprising delivering, by the first drivecircuit, the first energy modality until a tissue seal is formed.
 4. Amethod comprising: delivering, by a drive circuit, a first drive signalto an end effector of a surgical instrument at an amplitude; measuring,by a processor, a tissue coefficient of friction of tissue engaged withthe end effector; modulating, by the processor, delivery of the firstdrive signal based on the measured tissue coefficient of friction; andceasing, by the processor, delivery of the first drive signal when atermination parameter is met.
 5. The method of claim 4, wherein thefirst drive signal is a radiofrequency (RF) energy signal, and whereinthe amplitude is a therapeutic amplitude or a sub-therapeutic amplitude.6. The method of claim 4, further comprising determining that the tissueis sealed based on one of: initial tissue impedance; initial aperturedefined by jaws of the end effector; current tissue impedance; rate ofchange of tissue impedance; ultrasonic energy driven into the tissue;radiofrequency (RF) energy driven into the tissue; and transaction time.7. The method of claim 4, wherein the first drive signal is anultrasonic energy signal.
 8. The method of claim 4, wherein the firstdrive signal comprises a first energy signal, and wherein modulatingdelivery of the first energy signal comprises modifying an output powerof a generator, modifying an output waveform of the generator, selectinga second energy signal to deliver to the surgical instrument, ormodifying the termination parameter.
 9. The method of claim 4, furthercomprising ceasing delivery of the first drive signal upon the tissuecoefficient of friction matching a tissue coefficient of frictionthreshold value.
 10. The method of claim 4, wherein the first drivesignal comprises a first energy signal, wherein the amplitude is a firstamplitude, the method further comprising delivering a second drivesignal to tissue at a second amplitude.
 11. The method of claim 10,wherein the first drive signal is a radiofrequency (RF) energy signaland the second drive signal is an ultrasonic energy signal.
 12. Themethod of claim 4, wherein measuring the tissue coefficient of frictionfurther comprises measuring a rate of change of the tissue coefficientof friction.
 13. The method of claim 4, further comprising determining astate of the tissue based on the measured tissue coefficient offriction.
 14. The method of claim 13, wherein the state of the tissuecomprises coagulated, sealed, or cut.
 15. The method of claim 4, whereinmodulating delivery of the first drive signal to the end effector causesthe tissue coefficient of friction to change according to apredetermined technique.
 16. The method of claim 15, wherein thepredetermined technique comprises adjusting, by the processor, thetissue coefficient of friction according to a threshold value of thetissue coefficient of friction or a threshold rate of change of thetissue coefficient of friction.
 17. A method comprising: calculating, bya processor, a tissue coefficient of friction of tissue engaged with anend effector of a surgical instrument; comparing, by the processor, thecalculated tissue coefficient of friction with a coefficient of frictionthreshold value; delivering, by a radiofrequency (RF) drive circuit, RFenergy to an electrode of the end effector when the calculated tissuecoefficient of friction is less than the coefficient of frictionthreshold value; and delivering, by an ultrasonic drive circuit,ultrasonic energy to an ultrasonic blade of the end effector when thecalculated tissue coefficient of friction is greater than or equal tothe coefficient of friction threshold value.
 18. The method of claim 17,further comprising determining a type of energy to deliver to the endeffector to interact with the tissue by the end effector, wherein aproperty of the type of energy to be delivered corresponds to a type ofinteraction between the end effector and the tissue.
 19. The method ofclaim 17, wherein the RF energy and ultrasonic energy are delivered tothe end effector through a single output port of a generator that iselectrically coupled to the surgical instrument.